Positive resist compositions and patterning process

ABSTRACT

A polymer is obtained from (meth)acrylate having a bridged ring lactone group, (meth)acrylate having an acid-labile leaving group, and (meth)acrylate having a hydroxynaphthyl pendant. A positive resist composition comprising the polymer as a base resin, when exposed to high-energy radiation and developed, exhibits a high sensitivity, a high resolution, and a minimal line edge roughness due to controlled swell during development, and leaves minimal residues following development.

CROSS-REFERENCE TO RELATED APPLICATION

This non-provisional application claims priority under 35 U.S.C. §119(a)on Patent Application Nos. 2005-274163 and 2006-114084 filed in Japan onSep. 21, 2005 and Apr. 18, 2006, respectively, the entire contents ofwhich are hereby incorporated by reference.

TECHNICAL FIELD

This invention relates to positive resist compositions, typically of thechemical amplification type, adapted for exposure to high-energyradiation, which have a significantly high contrast of alkalidissolution rate before and after the exposure, a high sensitivity, ahigh resolution, a minimal line edge roughness, and good etchingresistance, and which are especially suited as micropatterning materialsfor the manufacture of VLSI or the formation of photomask patterns; anda patterning process using the same.

BACKGROUND OF THE INVENTION

In the drive for higher integration and operating speeds in LSI devices,the pattern rule is made drastically finer. The rapid advance towardfiner pattern rules is grounded on the development of a projection lenswith an increased NA, a resist material with improved performance, andexposure light of a shorter wavelength. In particular, the change-overfrom i-line (365 nm) to shorter wavelength KrF laser (248 nm) broughtabout a significant innovation, enabling mass-scale production of 0.18micron rule devices. To the demand for a resist material with a higherresolution and sensitivity, acid-catalyzed chemical amplificationpositive working resist materials are effective as disclosed in U.S.Pat. Nos. 4,491,628 and 5,310,619 (JP-B 2-27660 and JP-A 63-27829). Theynow become predominant resist materials especially adapted for deep UVlithography.

Resist materials adapted for KrF excimer lasers enjoyed early use on the0.3 micron process, passed through the 0.25 micron rule, and currentlyentered the mass production phase on the 0.18 micron rule. Engineershave started investigation on the 0.15 micron rule, with the trendtoward a finer pattern rule being accelerated. A wavelength change-overfrom KrF to shorter wavelength ArF excimer laser (193 nm) is expected toenable miniaturization of the design rule to 0.13 μm or less. Sinceconventionally used novolac resins and polyvinylphenol resins have verystrong absorption in proximity to 193 nm, they are difficult to use asthe base resin for resists. To ensure transparency and dry etchingresistance, some engineers investigated acrylic and alicyclic (typicallycycloolefin) resins as disclosed in JP-A 9-73173, JP-A 10-10739, JP-A9-230595 and WO 97/33198.

Among others, a focus is drawn on (meth)acrylic resin base resistsfeaturing a high resolution. One of the (meth)acrylic resins proposedthus far is a combination of (meth)acrylic units having methyladamantaneester as acid labile group units with (meth)acrylic units having lactonering ester as adhesive group units as disclosed in JP-A 9-90637.Norbornyl lactone is also proposed as an adhesive group having enhancedetching resistance as disclosed in JP-A 2000-26446, JP-A 2000-159758 andJP-A 2002-371114.

Of the outstanding tasks associated with the ArF lithography, it isdesired to minimize line edge roughness and to reduce residues followingdevelopment. One of the factors causing line edge roughness is swellingduring development. While the polyhydroxystyrene used as the resist forKrF lithography, in which the phenol moiety is a weak acidic group andhas an appropriate alkali solubility, is resistant to swelling, polymerscontaining hydrophobic cycloaliphatic groups, which must be dissolvedusing carboxylic acids having a high acidity, are likely to swell duringdevelopment.

Naphthalene ring is an aromatic having less absorption at wavelength 193nm. ArF resist compositions based on vinyl naphthalene copolymers aredescribed in J. Photopolym. Sci. Technol., Vol. 11, No. 3, p 489 (1998),JP-A 2004-163877, and JP-A 2002-107933. Since hydroxy-containingnaphthalene rings exhibit weak acidity like phenol, they are expected tobe effective in preventing swelling during development. Anotheradvantage of naphthalene ring is high etching resistance.

SUMMARY OF THE INVENTION

An object of the invention is to provide a positive resist compositionwhich when exposed to high-energy radiation and developed, exhibits ahigh sensitivity, a high resolution, and a minimal line edge roughnessdue to controlled swell during development, and leaves minimal residuesfollowing development. Another object of the invention is to provide aprocess for forming a pattern using the same.

In a first aspect, the invention provides a positive resist compositioncomprising a polymer comprising recurring units of the general formulae(a) and (b).

Herein R¹ is each independently hydrogen or methyl. R² is a hydroxygroup, acid labile group-substituted hydroxy group, carboxyl group, oracid labile group-substituted carboxyl group. R³ is an acid labile groupor lactone-containing adhesive group. X is a single bond or a straightor branched alkylene group of 1 to 6 carbon atoms which may have anester (—COO—) group or ether (—O—) group. The subscript m is 1 or 2, aand b are numbers in the range: 0<a<1.0 and 0<b≦0.8.

Preferred is a polymer comprising recurring units of the general formula(c) in addition to recurring units of the general formulae (a) and (b).

Herein R¹, R² and X are as defined above. R^(3A) is a lactone-containingadhesive group, and R^(3B) is an acid labile group. The subscript m is 1or 2, a, b and c are numbers in the range: 0<a<1.0, 0≦b≦0.8, 0≦c≦0.8,and 0<b+c≦0.8.

When exposed to high-energy radiation and developed, the positive resistcomposition comprising the above polymer as a base resin has asignificantly high contrast of alkali dissolution rate before and afterthe exposure, a high sensitivity, a high resolution, and a minimal lineedge roughness due to controlled swell during development, leavesminimal residues following etching, and exhibits good etchingresistance. Owing to these advantages, the composition is fullyacceptable in industrial practice and especially suited as amicropatterning material for the manufacture of VLSI or the formation ofphotomask patterns.

The composition is preferably formulated as a chemically amplifiedpositive resist composition comprising (A) the above polymer as a baseresin, (B) an organic solvent, and (C) a photoacid generator. With thisformulation, in the exposed area, the rate of dissolution of the polymerin a developer liquid is accelerated by acid-catalyzed reaction. Thenthe chemically amplified positive resist composition has so high asensitivity that it is very suitable as the micropatterning materialwhich is currently needed for the manufacture of VLSI. The positiveresist composition may further include a dissolution inhibitor. Theinclusion of a dissolution inhibitor enhances the difference indissolution rate between the exposed and unexposed areas, leading to afurther improvement in resolution. The positive resist composition mayfurther include a basic compound and/or a surfactant. The addition of abasic compound holds down the rate of diffusion of acid within theresist film, leading to a further improvement in resolution. Theaddition of a surfactant improves or controls the applicability of theresist composition.

A pattern may be formed on a semiconductor substrate or mask substrateusing the resist composition of the invention, typically by applying theresist composition onto a substrate to form a coating, heat treating thecoating, exposing it to high-energy radiation, and developing it with adeveloper liquid. Heat treatment may also be carried out after theexposure and before the development. The process may, of course, befollowed by various steps such as etching, resist removal and cleaningsteps. The high-energy radiation typically has a wavelength of up to 200nm. The resist composition containing the inventive polymer as the baseresin is especially effective for exposure to high-energy radiation witha wavelength of up to 200 nm because its sensitivity to the exposurewavelength in the range is very high.

BENEFITS OF THE INVENTION

The positive resist compositions of the invention have many advantagesincluding a high sensitivity, a high resolution, minimized line edgeroughness, minimal residues following development, and controlled swellduring development. There are thus provided positive resistcompositions, especially chemically amplified positive resistcompositions, which are suited as micropatterning materials for themanufacture of VLSI or the formation of photomask patterns.

DESCRIPTION OF THE PREFERRED EMBODIMENTS

The inventors continued research works targeting a positive resistcomposition which when exposed to high-energy radiation and developed,exhibits a high sensitivity, a high resolution, and a minimal line edgeroughness due to controlled swell during development, and leaves minimalresidues following development.

Polyhydroxystyrene used in the KrF excimer laser lithography, which hasphenol groups with an appropriate acidity, is characterized by minimalswell in an alkaline developer liquid. At the wavelength of 193 nm,benzene ring cannot be used because of its very strong absorption.Instead, it was proposed to use vinylnaphthalene having an absorptionmaximum shifted toward the longer wavelength side. Albeit lessabsorption than styrene, vinylnaphthalene still has a noticeableabsorption above the level for use in resist compositions, and so theproportion of incorporation is limited and the resist film must be thin.

As the problem that resist patterns collapse following developmentbecomes serious, an approach for thin resist film is in progress. Forthe 45-nm generation of lithography, a film thickness equal to or lessthan 150 nm is considered, but a concomitant drop of etching resistancebecomes serious. An increase of line edge roughness is also observedconcomitantly with the film thickness reduction. With the progress ofthin resist film, greater absorption of resist compositions is ratheradvantageous in avoiding inverse-tapered profiles. Also, in the case ofimplant resist compositions which are used with highly reflectivesubstrates, it is necessary to reduce the transmittance positively inorder to suppress substrate reflection. In the prior art, increasing theamount of photoacid generator (PAG) added is effective for transmittancereduction. However, an increase of the PAG addition amount beyond thenecessity leads to losses of characteristics including a lowering ofetching resistance, a lowering of resolution due to enhanced aciddiffusion, and an enlargement of proximity bias.

Intending to incorporate phenolic hydroxyl groups, the inventors havemade a study to incorporate (meth)acrylate having a hydroxynaphthylgroup as the adhesive group. The inventors have discovered that when itis further copolymerized with recurring units having lactone as theadhesive group, the resulting copolymer is endowed with a good balanceof hydrophilicity, alkaline solubility and adhesion. In particular, whena polymer which is obtained from a combination of (meth)acrylate havinga bridged ring lactone group, (meth)acrylate having an acid-labileleaving group, and (meth)acrylate having a hydroxynaphthyl pendant as anadhesive group is used as the base resin, there is provided a positiveresist composition which when exposed to high-energy radiation anddeveloped, exhibits a high sensitivity, a high resolution, and a minimalline edge roughness due to controlled swell during development, andleaves minimal residues following development. The composition also hasexcellent dry etching resistance.

Polymer

The positive resist composition of the invention comprises a polymer orhigh molecular weight compound comprising recurring units of the generalformulae (a) and (b).

Herein R¹ which may be the same or different is hydrogen or methyl. R²is a hydroxy group, an acid labile group-substituted hydroxy group, acarboxyl group, or an acid labile group-substituted carboxyl group. R³is an acid labile group or a lactone-containing adhesive group. X is asingle bond or a straight or branched alkylene group of 1 to 6 carbonatoms-which may have an ester (—COO—) group or ether (—O—) group. Thesubscript m is 1 or 2, a and b are numbers in the range: 0<a<1.0 and0<b≦0.8.

In a preferred embodiment, the polymer further comprises recurring unitsof the general formula (c). That is, the preferred polymer comprisesrecurring units of the general formulae (a), (b), and (c).

Herein R¹ which may be the same or different is hydrogen or methyl. R²is a hydroxy group, an acid labile group-substituted hydroxy group, acarboxyl group, or an acid labile group-substituted carboxyl group.R^(3A) is a lactone-containing adhesive group, and R^(3B) is an acidlabile group. X is a single bond or a straight or branched alkylenegroup of 1 to 6 carbon atoms which may have an ester group or ethergroup. The subscript m is 1 or 2, a, b and c are numbers in the range:0<a<1.0, 0≦b≦0.8, 0≦c≦0.8, and 0<b+c≦0.8.

When exposed to high-energy radiation and developed, the positive resistcomposition comprising the above polymer as a base resin has asignificantly high contrast of alkali dissolution rate before and afterthe exposure, a high sensitivity, a high resolution, and a minimal lineedge roughness due to controlled swell during development, leavesminimal residues following etching, and exhibits good etchingresistance. Owing to these advantages, the composition is fullyacceptable in industrial practice and especially suited as amicropatterning material for the manufacture of VLSI or the formation ofphotomask patterns.

Examples of the monomers “a” from which the recurring units of formula(a) are derived are given below.

Herein, R is a hydrogen atom or acid labile group. When the hydroxygroup is substituted by an acetyl group, the acetyl group can bedeblocked and converted to a hydroxy group through alkaline hydrolysisafter polymerization. When the hydroxy group is substituted by an acidlabile group such as acetal, the acid labile group can be deblocked andconverted to a hydroxy group through acid-catalyzed hydrolysis. Suchdeblocking after polymerization may be omitted.

The polymer of the invention should have copolymerized therein recurringunits of (meth)acrylate having a naphthyl group as represented byformula (a) and recurring units of (meth)acrylate having an acid labilegroup or lactone ring as represented by formula (b).

Examples of the monomers “b” from which the recurring units of formula(b) are derived are given below.

In order that the resist composition of the invention be positiveworking, advantageously the polymer has further copolymerized therein amonomer “c” having an acid labile group as represented by the followinggeneral formula.

Herein R¹ is as defined above, and R^(3B) is an acid labile group.

The acid labile groups represented by R and R^(3B) may be identical ordifferent and selected from a variety of such groups. Preferred arestructures in which the hydrogen atom of hydroxyl group or of hydroxylmoiety of carboxyl group is substituted with a group of formula (AL-10)or (AL-11), a tertiary alkyl group of 4 to 40 carbon atoms representedby formula (AL-12), an oxoalkyl group of 4 to 20 carbon atoms, or thelike.

In formulae (AL-10) and (AL-11), R⁵¹ and R⁵⁴ each are a monovalenthydrocarbon group, typically a straight, branched or cyclic alkyl groupof 1 to 40 carbon-atoms, especially 1 to 20 carbon atoms, which maycontain a heteroatom such as oxygen, sulfur, nitrogen or fluorine. Thesubscript n is an integer of 0 to 10. R⁵² and R⁵³ each are hydrogen or amonovalent hydrocarbon group, typically a straight, branched or cyclicC₁-C₂₀ alkyl group, which may contain a heteroatom such as oxygen,sulfur, nitrogen or fluorine. Alternatively, a pair of R⁵² and R⁵³, R⁵²and R⁵⁴, or R⁵³ and R⁵⁴ taken together, may form a ring with the carbonatom or the carbon and oxygen atoms to which they are attached, the ringhaving 3 to 20 carbon atoms, especially 4 to 16 carbon atoms.

In formula (AL-12), R⁵⁵, R⁵⁶ and R⁵⁷ each are a monovalent hydrocarbongroup, typically a straight, branched or cyclic C₁-C₂₀ alkyl group,which may contain a heteroatom such as oxygen, sulfur, nitrogen orfluorine. Alternatively, a pair of R⁵⁵ and R⁵⁶, R⁵⁵ and R⁵⁷ , or R⁵⁶ andR⁵⁷ , taken together, may form a ring with the carbon atom to which theyare attached, the ring having 3 to 20 carbon atoms, especially 4 to 16carbon atoms.

Illustrative examples of the groups of formula (AL-10) includetert-butoxycarbonyl, tert-butoxycarbonylmethyl, tert-amyloxycarbonyl,tert-amyloxycarbonylmethyl, 1-ethoxyethoxycarbonylmethyl,2-tetrahydropyranyloxycarbonylmethyl and2-tetrahydrofuranyloxycarbonylmethyl as well as substituent groups ofthe following formulae (AL-10)-1 to (AL-10)-10.

In formulae (AL-10)-1 to (AL-10)-10, R⁵⁸ is independently a straight,branched or cyclic C₁-C₈ alkyl group, C₆-C₂₀ aryl group or C₇-C₂₀aralkyl group; R⁵⁹ is hydrogen or a straight, branched or cyclic C₁-C₂₀alkyl group; R⁶⁰ is a C₆-C₂₀ aryl group or C₇-C₂₀ aralkyl group; and nis an integer of 0 to 10.

Illustrative examples of the acetal group of formula (AL-11) includethose of the following formulae (AL-11)-1 to (AL-11)-34.

The polymer may be crosslinked within the molecule or between moleculeswith acid labile groups of formula (AL-11a) or (AL-11b).

Herein R⁶¹ and R⁶² each are hydrogen or a straight, branched or cyclicC₁-C₈ alkyl group, or R⁶¹ and R⁶² ₁ taken together, may form a ring withthe carbon atom to which they are attached, and R⁶¹ and R⁶² are straightor branched C₁-C₈ alkylene groups when they form a ring. R⁶³ is astraight, branched or cyclic C₁-C₁₀ alkylene group. Each of p and r is 0or an integer of 1 to 10, preferably 0 or an integer of 1 to 5, and q isan integer of 1 to 7. “A” is a (q+1)-valent aliphatic or alicyclicsaturated hydrocarbon group, aromatic hydrocarbon group or heterocyclicgroup having 1 to 50 carbon atoms, which may be separated by aheteroatom such as oxygen, sulfur or nitrogen or in which some of thehydrogen atoms attached to carbon atoms may be substituted by hydroxyl,carboxyl, carbonyl groups or fluorine atoms. “B” is —CO—O—, —NHCO—O— or—NHCONH—.

Preferably, “A” is selected from divalent to tetravalent, straight,branched or cyclic C₁-C₂₀ alkylene, alkyltriyl and alkyltetrayl groups,and C₆-C₃₀ arylene groups, which may be separated by a heteroatom suchas oxygen, sulfur or nitrogen or in which some of the hydrogen atomsattached to carbon atoms may be substituted by hydroxyl, carboxyl, acylgroups or halogen atoms. The subscript q is preferably an integer of 1to 3.

The crosslinking acetal groups of formulae (AL-11a) and (AL-11b) areexemplified by the following formulae (AL-11)-35 through (AL-11)-42.

Illustrative examples of the tertiary alkyl of formula (AL-12) includetert-butyl, triethylcarbyl, 1-ethylnorbornyl, 1-methylcyclohexyl,1-ethylcyclopentyl, and tert-amyl groups as well as those of (AL-12)-1to (AL-12)-16.

Herein R⁶⁴ is independently a straight, branched or cyclic C₁-C₈ alkylgroup, C₆-C₂₀ aryl group or C₇-C₂₀ aralkyl group; R⁶⁵ and R⁶⁷ each arehydrogen or a straight, branched or cyclic C₁-C₂₀ alkyl group; and R⁶⁶is a C₆-C₂₀ aryl group or C₇-C₂₀ aralkyl group.

With R⁶⁸ representative of a di- or more valent alkylene or arylenegroup included as shown in formulae (AL-12)-17 and (AL-12)-18, thepolymer may be crosslinked within the molecule or between molecules. Informulae (AL-12)-17 and (AL-12)-18, R⁶⁴ is as defined above; R⁶⁸ is astraight, branched or cyclic C₁-C₂₀ alkylene group or arylene groupwhich may contain a heteroatom such as oxygen, sulfur or nitrogen; and sis an integer of 1 to 3.

The groups represented by R⁶⁴, R⁶⁵, R⁶⁶ and R⁶⁷ may contain a heteroatomsuch as oxygen, nitrogen or sulfur, examples of which are illustrated bythose of the following formulae (AL-13)-1 to (AL-13)-7.

Of the acid labile groups of formula (AL-12), recurring units having anexo-form structure represented by the formula (AL-12)-19 are preferred.

Herein, R⁶⁹ is a straight, branched or cyclic C₁-C₈ alkyl group or asubstituted or unsubstituted C₆-C₂₀ aryl group; R⁷⁰ to R⁷⁵, R⁷⁸ and R⁷⁹are each independently hydrogen or a monovalent hydrocarbon group of 1to 15 carbon atoms which may contain a heteroatom; and R⁷⁶ and R⁷⁷ arehydrogen. Alternatively, a pair of R⁷⁰ and R⁷¹, R⁷² and R⁷⁴, R⁷² andR⁷⁵, R⁷³ and R⁷⁵ , R⁷³ and R⁷⁹ , R⁷⁴ and R⁷⁸, R⁷⁶ and R⁷⁷ , or R⁷⁷ andR⁷⁸, taken together, may form a ring, and in this case, each R is adivalent hydrocarbon group of 1 to 15 carbon atoms which may contain aheteroatom. Also, a pair of R⁷⁰ and R⁷⁹, R⁷⁶ and R⁷⁹, or R⁷² and R⁷⁴which are attached to adjoining carbon atoms may bond together directlyto form a double bond. R⁷⁷ is hydrogen or a straight, branched or cyclicC₁-C₁₅ alkyl group. The formula also represents an enantiomer.

The ester form monomers from which recurring units having an exo-formstructure represented by the formula (AL-12)-19:

are derived are described in U.S. Pat. No. 6,448,420 (JP-A 2000-327633).Illustrative non-limiting examples of suitable monomers are given below.

Also included in the acid labile groups of formula (AL-12) are acidlabile groups having furandiyl, tetrahydrofurandiyl or oxanorbornanediylas represented by the following formula (AL-12)-20.

Herein, R⁸⁰ and R⁸¹ are each independently a straight, branched orcyclic, monovalent hydrocarbon group of 1 to 10 carbon atoms. R⁸⁰ andR⁸¹, taken together, may form an aliphatic hydrocarbon ring of 3 to 20carbon atoms with the carbon atom to which they are attached. R⁸² is adivalent group selected from furandiyl, tetrahydrofurandiyl andoxanorbornanediyl. R⁸³ is hydrogen or a straight, branched or cyclic,monovalent hydrocarbon group of 1 to 10 carbon atoms which may contain aheteroatom.

Examples of the monomers from which the recurring units substituted withacid labile groups having furandiyl, tetrahydrofurandiyl andoxanorbornanediyl as represented by the formula:

(wherein R⁸⁰, R⁸¹, R⁸² and R⁸³ are as defined above) are derived areshown below. Note that Me is methyl and Ac is acetyl.

While the polymer to be compounded in the resist composition of theinvention includes essentially recurring units of formulae (a) and (b)or formulae (a), (b) and (c), it may have copolymerized thereinrecurring units having adhesive groups other than formulae (a) and (c).Specifically, recurring units “d” derived from monomers, listed below,may be incorporated.

In the polymer of the invention, the recurring units “a”, “b”, “c” and“d” are present in proportions which satisfy the range: 0<a<1.0,0<b≦0.8, 0≦c≦0.8, 0<b+c≦0.8, and 0≦d≦0.8, preferably 0.01≦a≦0.9,0.05≦b≦0.7, 0.05≦c≦0.7, and 0≦d≦0.7. Understandably, it is preferredthat the sum of a+b+c+d be equal to 1. For a polymer comprisingrecurring units a, b, c and d, a+b+c+d=1 means that the total ofrecurring units a, b, c and d is 100 mol % relative to the total ofentire recurring units.

The polymer of the invention should preferably have a weight averagemolecular weight (Mw) in the range of 1,000 to 500,000, more preferably2,000 to 30,000 as measured by gel permeation chromatography (GPC) usingpolystyrene standards. With too low a Mw, the resist composition may beless heat resistant. With too high a Mw, the resist composition may losealkali solubility and give rise to a footing phenomenon after patternformation.

If a polymer has a wide molecular weight distribution or dispersity(Mw/Mn), which indicates the presence of lower and higher molecularweight polymer components, there is a possibility that foreign matter isleft on the pattern or the pattern profile is degraded. The influencesof molecular weight and dispersity become stronger as the pattern rulebecomes finer. Therefore, the multi-component copolymer shouldpreferably have a narrow dispersity (Mw/Mn) of 1.0 to 2.0, especially1.0 to 1.5, in order to provide a resist composition suitable formicropatterning to a small feature size.

It is understood that on use of the polymer as the base resin, a blendof two or more polymers which differ in compositional ratio, molecularweight or dispersity is acceptable.

The polymer of the invention may be synthesized by any desired method,for example, by dissolving unsaturated bond-containing monomerscorresponding to the respective units “a”, “b”, “c” and “d” in anorganic solvent, adding a radical initiator thereto, and effecting heatpolymerization. Examples of the organic solvent which can be used forpolymerization include toluene, benzene, tetrahydrofuran, diethyl etherand dioxane. Examples of the polymerization initiator used hereininclude 2,2′-azobisisobutyronitrile (AIBN),2,2′-azobis(2,4-dimethylvaleronitrile), dimethyl2,2-azobis(2-methylpropionate), benzoyl peroxide, and lauroyl peroxide.Preferably the system is heated at 50 to 80° C. for polymerization totake place. The reaction time is about 2 to 100 hours, preferably about5 to 20 hours. The acid labile group that has been incorporated in themonomers may be kept as such, or the acid labile group may be onceremoved with an acid catalyst and thereafter protected or partiallyprotected.

In addition to the polymer, the positive resist composition, especiallychemically amplified positive resist composition of the invention maycomprise an organic solvent, a compound capable of generating an acid inresponse to high-energy radiation (photoacid generator), and optionally,a dissolution inhibitor, a basic compound, a surfactant and otheradditives.

Solvent

The organic solvent used herein may be any organic solvent in which thebase resin, photoacid generator, and other components are soluble.Illustrative, non-limiting, examples of the organic solvent includeketones such as cyclohexanone and methyl-2-n-amylketone; alcohols suchas 3-methoxybutanol, 3-methyl-3-methoxybutanol, 1-methoxy-2-propanol,and 1-ethoxy-2-propanol; ethers such as propylene glycol monomethylether, ethylene glycol monomethyl ether, propylene glycol monoethylether, ethylene glycol monoethyl ether, propylene glycol dimethyl ether,and diethylene glycol dimethyl ether; esters such as propylene glycolmonomethyl ether acetate, propylene glycol monoethyl ether acetate,ethyl lactate, ethyl pyruvate, butyl acetate, methyl3-methoxypropionate, ethyl 3-ethoxypropionate, tert-butyl acetate,tert-butyl propionate, and propylene glycol mono-tert-butyl etheracetate; and lactones such as γ-butyrolactone. These solvents may beused alone or in combinations of two or more thereof. Of the aboveorganic solvents, diethylene glycol dimethyl ether, 1-ethoxy-2-propanoland propylene glycol monomethyl ether acetate, and mixtures thereof arepreferred because the photoacid generator is most soluble therein.

The organic solvent is preferably used in an amount of about 200 to1,000 parts by weight, more preferably about 400 to 800 parts by weightper 100 parts by weight of the base resin.

Photoacid Generator

The photoacid generator is a compound capable of generating an acid uponexposure to high-energy radiation and includes the following:

-   (i) onium salts of the formula (P1a-1), (P1a-2) or (P1b),-   (ii) diazomethane derivatives of the formula (P2),-   (iii) glyoxime derivatives of the formula (P3),-   (iv) bissulfone derivatives of the formula (P4),-   (v) sulfonic acid esters of N-hydroxyimide compounds of the formula    (P5),-   (vi) β-ketosulfonic acid derivatives,-   (vii) disulfone derivatives,-   (viii) nitrobenzylsulfonate derivatives, and-   (ix) sulfonate derivatives.

These photoacid generators are described in detail.

(i) Onium salts of formula (P1a-1), (P1a-2) or (P1b):

Herein, R^(101a), R^(101b), and R^(101c) independently representstraight, branched or cyclic alkyl, alkenyl, oxoalkyl or oxoalkenylgroups of 1 to 12 carbon atoms, aryl groups of 6 to 20 carbon atoms, oraralkyl or aryloxoalkyl groups of 7 to 12 carbon atoms, wherein some orall of the hydrogen atoms may be replaced by alkoxy or other groups.Also, R^(101b) and R^(101c), taken together, may form a ring. R^(101b)and R^(101c) each are an alkylene group of 1 to 6 carbon atoms when theyform a ring. K³¹ is a non-nucleophilic counter ion.

R^(101a), R^(101b), and R^(101c) may be the same or different and areillustrated below. Exemplary alkyl groups include methyl, ethyl, propyl,isopropyl, n-butyl, sec-butyl, tert-butyl, pentyl, hexyl, heptyl, octyl,cyclopentyl, cyclohexyl, cycloheptyl, cyclopropylmethyl,4-methylcyclohexyl, cyclohexylmethyl, norbornyl, and adamantyl.Exemplary alkenyl groups include vinyl, allyl, propenyl, butenyl,hexenyl, and cyclohexenyl. Exemplary oxoalkyl groups include2-oxocyclopentyl and 2-oxocyclohexyl as well as 2-oxopropyl,2-cyclopentyl-2-oxoethyl, 2-cyclohexyl-2-oxoethyl, and2-(4-methylcyclohexyl)-2-oxoethyl. Exemplary oxoalkenyl groups include2-oxo-4-cyclohexenyl and 2-oxo-4-propenyl. Exemplary aryl groups includephenyl and naphthyl; alkoxyphenyl groups such as p-methoxyphenyl,m-methoxyphenyl, o-methoxyphenyl, ethoxyphenyl, p-tert-butoxyphenyl, andm-tert-butoxyphenyl; alkylphenyl groups such as 2-methylphenyl,3-methylphenyl, 4-methylphenyl, ethylphenyl, 4-tert-butylphenyl,4-butylphenyl, and dimethylphenyl; alkylnaphthyl groups such asmethylnaphthyl and ethylnaphthyl; alkoxynaphthyl groups such asmethoxynaphthyl and ethoxynaphthyl; dialkylnaphthyl groups such asdimethylnaphthyl and diethylnaphthyl; and dialkoxynaphthyl groups suchas dimethoxynaphthyl and diethoxynaphthyl. Exemplary aralkyl groupsinclude benzyl, phenylethyl, and phenethyl. Exemplary aryloxoalkylgroups are 2-aryl-2-oxoethyl groups such as 2-phenyl-2-oxoethyl,2-(1-naphthyl)-2-oxoethyl, and 2-(2-naphthyl)-2-oxoethyl. Examples ofthe non-nucleophilic counter ion represented by K⁻ include halide ionssuch as chloride and bromide ions, fluoroalkylsulfonate ions such astriflate, 1,1,1-trifluoroethanesulfonate, and nonafluorobutanesulfonate,arylsulfonate ions such as tosylate, benzenesulfonate,4-fluorobenzenesulfonate, and 1,2,3,4,5-pentafluorobenzenesulfonate, andalkylsulfonate ions such as mesylate and butanesulfonate.

Herein, R^(102a) and R^(102b) independently represent straight, branchedor cyclic alkyl groups of 1 to 8 carbon atoms. R¹⁰³ represents astraight, branched or cyclic alkylene group of 1 to 10 carbon atoms.R^(104a) and R^(104b) independently represent 2-oxoalkyl groups of 3 to7 carbon atoms. K⁻ is a non-nucleophilic counter ion.

Illustrative of the groups represented by R^(102a) and R^(102b) aremethyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl, tert-butyl,pentyl, hexyl, heptyl, octyl, cyclopentyl, cyclohexyl,cyclopropylmethyl, 4-methylcyclohexyl, and cyclohexylmethyl.Illustrative of the groups represented by R¹⁰³ are methylene, ethylene,propylene, butylene, pentylene, hexylene, heptylene, octylene, nonylene,1,4-cyclohexylene, 1,2-cyclohexylene, 1,3-cyclopentylene,1,4-cyclooctylene, and 1,4-cyclohexanedimethylene. Illustrative of thegroups represented by R^(104a) and R^(104b) are 2-oxopropyl,2-oxocyclopentyl, 2-oxocyclohexyl, and 2-oxocycloheptyl. Illustrativeexamples of the counter ion represented by K⁻ are the same asexemplified for formulae (P1a-1) and (P1a-2).

(ii) Diazomethane Derivatives of Formula (P2)

Herein, R¹⁰⁵ and R¹⁰⁶ independently represent straight, branched orcyclic alkyl or halogenated alkyl groups of 1 to 12 carbon atoms, arylor halogenated aryl groups of 6 to 20 carbon atoms, or aralkyl groups of7 to 12 carbon atoms.

Of the groups represented by R¹⁰⁵ and R¹⁰⁶, exemplary alkyl groupsinclude methyl, ethyl, propyl, isopropyl, n-butyl, sec-butyl,tert-butyl, pentyl, hexyl, heptyl, octyl, amyl, cyclopentyl, cyclohexyl,cycloheptyl, norbornyl, and adamantyl. Exemplary halogenated alkylgroups include trifluoromethyl, 1,1,1-trifluoroethyl,1,1,1-trichloroethyl, and nonafluorobutyl. Exemplary aryl groups includephenyl; alkoxyphenyl groups such as p-methoxyphenyl, m-methoxyphenyl,o-methoxyphenyl, ethoxyphenyl, p-tert-butoxyphenyl, andm-tert-butoxyphenyl; and alkylphenyl groups such as 2-methylphenyl,3-methylphenyl, 4-methylphenyl, ethylphenyl, 4-tert-butylphenyl,4-butylphenyl, and dimethylphenyl. Exemplary halogenated aryl groupsinclude fluorophenyl, chlorophenyl, and 1,2,3,4,5-pentafluorophenyl.Exemplary aralkyl groups include benzyl and phenethyl.

(iii) Glyoxime Derivatives of Formula (P3)

Herein, R¹⁰⁷, R¹⁰⁸, and R¹⁰⁹ independently represent straight, branchedor cyclic alkyl or halogenated alkyl groups of 1 to 12 carbon atoms,aryl or halogenated aryl groups of 6 to 20 carbon atoms, or aralkylgroups of 7 to 12 carbon atoms. Also, R¹⁰⁸ and R¹⁰⁹, taken together, mayform a ring. R¹⁰⁸ and R¹⁰⁹ each are a straight or branched alkylenegroup of 1 to 6 carbon atoms when they form a ring. R¹⁰⁵ is as definedin formula (P2).

Illustrative examples of the alkyl, halogenated alkyl, aryl, halogenatedaryl, and aralkyl groups represented by R¹⁰⁷, R¹⁰⁸, and R¹⁰⁹ are thesame as exemplified for R¹⁰⁵ and R¹⁰⁶. Examples of the alkylene groupsrepresented by R¹⁰⁸ and R¹⁰⁹ include methylene, ethylene, propylene,butylene, and hexylene.

(iv) Bissulfone Derivatives of Formula (P4)

Herein, R^(101a) and R^(101b) are as defined above.

(v) Sulfonic Acid Esters of N-Hydroxyimide Compounds of Formula (P5)

Herein, R¹¹⁰ is an arylene group of 6 to 10 carbon atoms, alkylene groupof 1 to 6 carbon atoms, or alkenylene group of 2 to 6 carbon atomswherein some or all of the hydrogen atoms may be replaced by straight orbranched alkyl or alkoxy groups of 1 to 4 carbon atoms, nitro, acetyl,or phenyl groups. R¹¹¹ is a straight, branched or cyclic alkyl group of1 to 8 carbon atoms, alkenyl, alkoxyalkyl, phenyl or naphthyl groupwherein some or all of the hydrogen atoms may be replaced by alkyl oralkoxy groups of 1 to 4 carbon atoms, phenyl groups (which may havesubstituted thereon an alkyl or alkoxy of 1 to 4 carbon atoms, nitro, oracetyl group), hetero-aromatic groups of 3 to 5 carbon atoms, orchlorine or fluorine atoms.

Of the groups represented by R¹¹⁰, exemplary arylene groups include1,2-phenylene and 1,8-naphthylene; exemplary alkylene groups includemethylene, ethylene, trimethylene, tetramethylene, phenylethylene, andnorbornane-2,3-diyl; and exemplary alkenylene groups include1,2-vinylene, 1-phenyl-1,2-vinylene, and 5-norbornene-2,3-diyl. Of thegroups represented by R¹¹¹, exemplary alkyl groups are as exemplifiedfor R^(101a) to R^(101c); exemplary alkenyl groups include vinyl,1-propenyl, allyl, 1-butenyl, 3-butenyl, isoprenyl, 1-pentenyl,3-pentenyl, 4-pentenyl, dimethylallyl, 1-hexenyl, 3-hexenyl, 5-hexenyl,1-heptenyl, 3-heptenyl, 6-heptenyl, and 7-octenyl; and exemplaryalkoxyalkyl groups include methoxymethyl, ethoxymethyl, propoxymethyl,butoxymethyl, pentyloxymethyl, hexyloxymethyl, heptyloxymethyl,methoxyethyl, ethoxyethyl, propoxyethyl, butoxyethyl, pentyloxyethyl,hexyloxyethyl, methoxypropyl, ethoxypropyl, propoxypropyl, butoxypropyl,methoxybutyl, ethoxybutyl, propoxybutyl, methoxypentyl, ethoxypentyl,methoxyhexyl, and methoxyheptyl.

Of the substituents on these groups, the alkyl groups of 1 to 4 carbonatoms include methyl, ethyl, propyl, isopropyl, n-butyl, isobutyl andtert-butyl; and the alkoxy groups of 1 to 4 carbon atoms includemethoxy, ethoxy, propoxy, isopropoxy, n-butoxy, isobutoxy, andtert-butoxy. The phenyl groups which may have substituted thereon analkyl or alkoxy of 1 to 4 carbon atoms, nitro, or acetyl group includephenyl, tolyl, p-tert-butoxyphenyl, p-acetylphenyl and p-nitrophenyl.The hetero-aromatic groups of 3 to 5 carbon atoms include pyridyl andfuryl.

Illustrative examples of the photoacid generator include:

onium salts such as

-   diphenyliodonium trifluoromethanesulfonate,-   (p-tert-butoxyphenyl)phenyliodonium trifluoromethanesulfonate,-   diphenyliodonium p-toluenesulfonate,-   (p-tert-butoxyphenyl)phenyliodonium p-toluenesulfonate,-   triphenylsulfonium trifluoromethanesulfonate,-   (p-tert-butoxyphenyl)diphenylsulfonium trifluoromethane-sulfonate,-   bis(p-tert-butoxyphenyl)phenylsulfonium trifluoromethane-sulfonate,-   tris(p-tert-butoxyphenyl)sulfonium trifluoromethanesulfonate,-   triphenylsulfonium p-toluenesulfonate,-   (p-tert-butoxyphenyl)diphenylsulfonium p-toluenesulfonate,-   bis(p-tert-butoxyphenyl)phenylsulfonium p-toluenesulfonate,-   tris(p-tert-butoxyphenyl)sulfonium p-toluenesulfonate,-   triphenylsulfonium nonafluorobutanesulfonate,-   triphenylsulfonium butanesulfonate,-   trimethylsulfonium trifluoromethanesulfonate,-   trimethylsulfonium p-toluenesulfonate,-   cyclohexylmethyl(2-oxocyclohexyl)sulfonium    trifluoromethane-sulfonate,-   cyclohexylmethyl(2-oxocyclohexyl)sulfonium p-toluenesulfonate,-   dimethylphenylsulfonium trifluoromethanesulfonate,-   dimethylphenylsulfonium p-toluenesulfonate,-   dicyclohexylphenylsulfonium trifluoromethanesulfonate,-   dicyclohexylphenylsulfonium p-toluenesulfonate,-   trinaphthylsulfonium trifluoromethanesulfonate,-   (2-norbornyl)methyl(2-oxocyclohexyl)sulfonium    trifluoro-methanesulfonate,-   ethylenebis[methyl(2-oxocyclopentyl)sulfonium    trifluoro-methanesulfonate], and-   1,2′-naphthylcarbonylmethyltetrahydrothiophenium triflate;

diazomethane derivatives such as

-   bis(benzenesulfonyl)diazomethane,-   bis(p-toluenesulfonyl)diazomethane,-   bis(xylenesulfonyl)diazomethane,-   bis(cyclohexylsulfonyl)diazomethane,-   bis(cyclopentylsulfonyl)diazomethane,-   bis(n-butylsulfonyl)diazomethane,-   bis(isobutylsulfonyl)diazomethane,-   bis(sec-butylsulfonyl)diazomethane,-   bis(n-propylsulfonyl)diazomethane,-   bis(isopropylsulfonyl)diazomethane,-   bis(tert-butylsulfonyl)diazomethane,-   bis(n-amylsulfonyl)diazomethane,-   bis(isoamylsulfonyl)diazomethane,-   bis(sec-amylsulfonyl)diazomethane,-   bis(tert-amylsulfonyl)diazomethane,-   1-cyclohexylsulfonyl-1-(tert-butylsulfonyl)diazomethane,-   1-cyclohexylsulfonyl-1-(tert-amylsulfonyl)diazomethane, and-   1-tert-amylsulfonyl-1-(tert-butylsulfonyl)diazomethane;

glyoxime derivatives such as

-   bis-O-(p-toluenesulfonyl)-α-dimethylglyoxime,-   bis-O-(p-toluenesulfonyl)-α-diphenylglyoxime,-   bis-O-(p-toluenesulfonyl)-α-dicyclohexylglyoxime,-   bis-O-(p-toluenesulfonyl)-2,3-pentanedioneglyoxime,-   bis-O-(p-toluenesulfonyl)-2-methyl-3,4-pentanedioneglyoxime,-   bis-O-(n-butanesulfonyl)-α-dimethylglyoxime,-   bis-O-(n-butanesulfonyl)-α-diphenylglyoxime,-   bis-O-(n-butanesulfonyl)-α-dicyclohexylglyoxime,-   bis-O-(n-butanesulfonyl)-2,3-pentanedioneglyoxime,-   bis-O-(n-butanesulfonyl)-2-methyl-3,4-pentanedioneglyoxime,-   bis-O-(methanesulfonyl)-α-dimethylglyoxime,-   bis-O-(trifluoromethanesulfonyl)-α-dimethylglyoxime,-   bis-O-(1,1,1-trifluoroethanesulfonyl)-α-dimethylglyoxime,-   bis-O-(tert-butanesulfonyl)-α-dimethylglyoxime,-   bis-O-(perfluorooctanesulfonyl)-α-dimethylglyoxime,-   bis-O-(cyclohexanesulfonyl)-α-dimethylglyoxime,-   bis-O-(benzenesulfonyl)-α-dimethylglyoxime,-   bis-O-(p-fluorobenzenesulfonyl)-α-dimethylglyoxime,-   bis-O-(p-tert-butylbenzenesulfonyl)-α-dimethylglyoxime,-   bis-O-(xylenesulfonyl)-α-dimethylglyoxime, and-   bis-O-(camphorsulfonyl)-α-dimethylglyoxime;

bissulfone derivatives such as

-   bisnaphthylsulfonylmethane, bistrifluoromethylsulfonylmethane,-   bismethylsulfonylmethane, bisethylsulfonylmethane,-   bispropylsulfonylmethane, bisisopropylsulfonylmethane,-   bis-p-toluenesulfonylmethane, and bisbenzenesulfonylmethane;

β-ketosulfone derivatives such as

-   2-cyclohexylcarbonyl-2-(p-toluenesulfonyl)propane and-   2-isopropylcarbonyl-2-(p-toluenesulfonyl)propane;

disulfone derivatives such as diphenyl disulfone deratives anddicyclohexyl disulfone derivatives;

nitrobenzyl sulfonate derivatives such as

-   2,6-dinitrobenzyl p-toluenesulfonate and-   2,4-dinitrobenzyl p-toluenesulfonate;

sulfonic acid ester derivatives such as

-   1,2,3-tris(methanesulfonyloxy)benzene,-   1,2,3-tris(trifluoromethanesulfonyloxy)benzene, and-   1,2,3-tris(p-toluenesulfonyloxy)benzene; and

sulfonic acid esters of N-hydroxyimides such as

-   N-hydroxysuccinimide methanesulfonate,-   N-hydroxysuccinimide trifluoromethanesulfonate,-   N-hydroxysuccinimide ethanesulfonate,-   N-hydroxysuccinimide 1-propanesulfonate,-   N-hydroxysuccinimide 2-propanesulfonate,-   N-hydroxysuccinimide 1-pentanesulfonate,-   N-hydroxysuccinimide 1-octanesulfonate,-   N-hydroxysuccinimide p-toluenesulfonate,-   N-hydroxysuccinimide p-methoxybenzenesulfonate,-   N-hydroxysuccinimide 2-chloroethanesulfonate,-   N-hydroxysuccinimide benzenesulfonate,-   N-hydroxysuccinimide 2,4,6-trimethylbenzenesulfonate,-   N-hydroxysuccinimide 1-naphthalenesulfonate,-   N-hydroxysuccinimide 2-naphthalenesulfonate,-   N-hydroxy-2-phenylsuccinimide methanesulfonate,-   N-hydroxymaleimide methanesulfonate,-   N-hydroxymaleimide ethanesulfonate,-   N-hydroxy-2-phenylmaleimide methanesulfonate,-   N-hydroxyglutarimide methanesulfonate,-   N-hydroxyglutarimide benzenesulfonate,-   N-hydroxyphthalimide methanesulfonate,-   N-hydroxyphthalimide benzenesulfonate,-   N-hydroxyphthalimide trifluoromethanesulfonate,-   N-hydroxyphthalimide p-toluenesulfonate,-   N-hydroxynaphthalimide methanesulfonate,-   N-hydroxynaphthalimide benzenesulfonate,-   N-hydroxy-5-norbornene-2,3-dicarboxyimide methanesulfonate,-   N-hydroxy-5-norbornene-2,3-dicarboxyimide    trifluoromethane-sulfonate, and-   N-hydroxy-5-norbornene-2,3-dicarboxyimide p-toluenesulfonate.

Preferred among these photoacid generators are onium salts such astriphenylsulfonium trifluoromethanesulfonate,

-   (p-tert-butoxyphenyl)diphenylsulfonium trifluoromethane-sulfonate,-   tris(p-tert-butoxyphenyl)sulfonium trifluoromethanesulfonate,-   triphenylsulfonium p-toluenesulfonate,-   (p-tert-butoxyphenyl)diphenylsulfonium p-toluenesulfonate,-   tris(p-tert-butoxyphenyl)sulfonium p-toluenesulfonate,-   trinaphthylsulfonium trifluoromethanesulfonate,-   cyclohexylmethyl(2-oxocyclohexyl)sulfonium    trifluoromethane-sulfonate,-   (2-norbornyl)methyl(2-oxocylohexyl)sulfonium    trifluoro-methanesulfonate, and-   1,2′-naphthylcarbonylmethyltetrahydrothiophenium triflate;-   diazomethane derivatives such as-   bis(benzenesulfonyl)diazomethane,-   bis(p-toluenesulfonyl)diazomethane,-   bis(cyclohexylsulfonyl)diazomethane,-   bis(n-butylsulfonyl)diazomethane,-   bis(isobutylsulfonyl)diazomethane,-   bis(sec-butylsulfonyl)diazomethane,-   bis(n-propylsulfonyl)diazomethane,-   bis(isopropylsulfonyl)diazomethane, and-   bis(tert-butylsulfonyl)diazomethane;-   glyoxime derivatives such as-   bis-O-(p-toluenesulfonyl)-α-dimethylglyoxime and-   bis-O-(n-butanesulfonyl)-α-dimethylglyoxime;-   bissulfone derivatives such as bisnaphthylsulfonylmethane;-   and sulfonic acid esters of N-hydroxyimide compounds such as    N-hydroxysuccinimide methanesulfonate,-   N-hydroxysuccinimide trifluoromethanesulfonate,-   N-hydroxysuccinimide 1-propanesulfonate,-   N-hydroxysuccinimide 2-propanesulfonate,-   N-hydroxysuccinimide 1-pentanesulfonate,-   N-hydroxysuccinimide p-toluenesulfonate,-   N-hydroxynaphthalimide methanesulfonate, and-   N-hydroxynaphthalimide benzenesulfonate.

These photoacid generators may be used singly or in combinations of twoor more thereof. Onium salts are effective for improving rectangularity,while diazomethane derivatives and glyoxime derivatives are effectivefor reducing standing waves. The combination of an onium salt with adiazomethane or a glyoxime derivative allows for fine adjustment of theprofile.

The photoacid generator is preferably added in an amount of 0.1 to 50parts, and especially 0.5 to 40 parts by weight, per 100 parts by weightof the base resin. Less than 0.1 part of the photoacid generator maygenerate a less amount of acid upon exposure, sometimes leading to apoor sensitivity and resolution whereas more than 50 parts of thephotoacid generator may adversely affect the transmittance andresolution of resist.

Dissolution Regulator

To the resist composition, a dissolution regulator or inhibitor may beadded. The dissolution regulator is a compound having on the molecule atleast two phenolic hydroxyl groups, in which an average of from 0 to 100mol % of all the hydrogen atoms on the phenolic hydroxyl groups arereplaced with acid labile groups or a compound having on the molecule atleast one carboxyl group, in which an average of 50 to 100 mol % of allthe hydrogen atoms on the carboxyl groups are replaced with acid labilegroups, both the compounds having a weight average molecular weightwithin a range of 100 to 1,000, and preferably 150 to 800.

The degree of substitution of the hydrogen atoms on the phenolichydroxyl groups with acid labile groups is on average at least 0 mol %,and preferably at least 30 mol %, of all the phenolic hydroxyl groups.The upper limit is 100 mol %, and preferably 80 mol %. The degree ofsubstitution of the hydrogen atoms on the carboxyl groups with acidlabile groups is on average at least 50 mol %, and preferably at least70 mol %, of all the carboxyl groups, with the upper limit being 100 mol%.

Preferable examples of such compounds having two or more phenolichydroxyl groups or compounds having at least one carboxyl group includethose of formulas (D1) to (D14) below.

In these formulas, R²⁰¹ and R²⁰² are each hydrogen or a straight orbranched C₁-C₈ alkyl or alkenyl; R²⁰³ is hydrogen, a straight orbranched C₁-C₈ alkyl or alkenyl, or —(R²⁰⁷)_(h)—COOH; R²⁰⁴ is—(CH₂)_(i)- (where i=2 to 10), a C₆-C₁₀ arylene, carbonyl, sulfonyl, anoxygen atom, or a sulfur atom; R²⁰⁵ is a C₁-C₁₀ alkylene, a C₆-C₁₀arylene, carbonyl, sulfonyl, an oxygen atom, or a sulfur atom; R²⁰⁶ ishydrogen, a straight or branched C₁-C₈ alkyl or alkenyl, or ahydroxyl-substituted phenyl or naphthyl; R²⁰⁷ is a straight or branchedC₁-C₁₀ alkylene; R²⁰⁸ is hydrogen or hydroxyl; the letter j is aninteger from 0 to 5; u and h are each 0 or 1; s, t, s′, t′, s″, and t″are each numbers which satisfy s+t=8, s′+t′=5, and s″+t″=4, and are suchthat each phenyl structure has at least one hydroxyl group; and α is anumber such that the compounds of formula (D8) or (D9) have a molecularweight of from 100 to 1,000.

The dissolution inhibitor may be formulated in an amount of 0 to 50parts, preferably 5 to 50 parts, and more preferably 10 to 30 parts byweight, per 100 parts by weight of the base resin, and may be usedsingly or as a mixture of two or more thereof. An appropriate amount ofthe dissolution inhibitor is effective for improving resolution whereasmore than 50 parts would lead to slimming of the patterned film, andthus a decline in resolution.

Basic Compound

The basic compound used herein is preferably a compound capable ofsuppressing the rate of diffusion when the acid generated by thephotoacid generator diffuses within the resist film. The inclusion ofthis type of basic compound holds down the rate of acid diffusion withinthe resist film, resulting in better resolution. In addition, itsuppresses changes in sensitivity following exposure, thus reducingsubstrate and environment dependence, as well as improving the exposurelatitude and the pattern profile.

Examples of suitable basic compounds include primary, secondary, andtertiary aliphatic amines, mixed amines, aromatic amines, heterocyclicamines, nitrogen-containing compounds having carboxyl group,nitrogen-containing compounds having sulfonyl group, nitrogen-containingcompounds having hydroxyl group, nitrogen-containing compounds havinghydroxyphenyl group, nitrogen-containing alcoholic compounds, amidederivatives, and imide derivatives.

Examples of suitable primary aliphatic amines include ammonia,methylamine, ethylamine, n-propylamine, isopropylamine, n-butylamine,iso-butylamine, sec-butylamine, tert-butylamine, pentylamine,tert-amylamine, cyclopentylamine, hexylamine, cyclohexylamine,heptylamine, octylamine, nonylamine, decylamine, dodecylamine,cetylamine, methylenediamine, ethylenediamine, andtetraethylenepentamine. Examples of suitable secondary aliphatic aminesinclude dimethylamine, diethylamine, di-n-propylamine,di-iso-propylamine, di-n-butylamine, di-iso-butylamine,di-sec-butylamine, dipentylamine, dicyclopentylamine, dihexylamine,dicyclohexylamine, diheptylamine, dioctylamine, dinonylamine,didecylamine, didodecylamine, dicetylamine,N,N-dimethylmethylenediamine, N,N-dimethylethylenediamine, andN,N-dimethyltetraethylenepentamine. Examples of suitable tertiaryaliphatic amines include trimethylamine, triethylamine,tri-n-propylamine, tri-iso-propylamine, tri-n-butylamine,tri-iso-butylamine, tri-sec-butylamine, tripentylamine,tricyclopentylamine, trihexylamine, tricyclohexylamine, triheptylamine,trioctylamine, trinonylamine, tridecylamine, tridodecylamine,tricetylamine, N,N,N′,N′-tetramethylmethylenediamine,N,N,N′,N′-tetramethylethylenediamine, andN,N,N′,N′-tetramethyltetraethylenepentamine.

Examples of suitable mixed amines include dimethylethylamine,methylethylpropylamine, benzylamine, phenethylamine, andbenzyldimethylamine. Examples of suitable aromatic amines includeaniline derivatives (e.g., aniline, N-methylaniline, N-ethylaniline,N-propylaniline, N,N-dimethylaniline, 2-methylaniline, 3-methylaniline,4-methylaniline, ethylaniline, propylaniline, trimethylaniline,2-nitroaniline, 3-nitroaniline, 4-nitroaniline, 2,4-dinitroaniline,2,6-dinitroaniline, 3,5-dinitroaniline, and N,N-dimethyltoluidine),diphenyl(p-tolyl)amine, methyldiphenylamine, triphenylamine,phenylenediamine, naphthylamine, and diaminonaphthalene. Examples ofsuitable heterocyclic amines include pyrrole derivatives (e.g., pyrrole,2H-pyrrole, 1-methylpyrrole, 2,4-dimethylpyrrole, 2,5-dimethylpyrrole,and N-methylpyrrole), oxazole derivatives (e.g., oxazole andisooxazole), thiazole derivatives (e.g., thiazole and isothiazole),imidazole derivatives (e.g., imidazole, 4-methylimidazole, and4-methyl-2-phenylimidazole), pyrazole derivatives, furazan derivatives,pyrroline derivatives (e.g., pyrroline and 2-methyl-1-pyrroline),pyrrolidine derivatives (e.g., pyrrolidine, N-methylpyrrolidine,pyrrolidinone, and N-methylpyrrolidone), imidazoline derivatives,imidazolidine derivatives, pyridine derivatives (e.g., pyridine,methylpyridine, ethylpyridine, propylpyridine, butylpyridine,4-(1-butylpentyl)pyridine, dimethylpyridine, trimethylpyridine,triethylpyridine, phenylpyridine, 3-methyl-2-phenylpyridine,4-tert-butylpyridine, diphenylpyridine, benzylpyridine, methoxypyridine,butoxypyridine, dimethoxypyridine, 1-methyl-2-pyridone,4-pyrrolidinopyridine, 1-methyl-4-phenylpyridine,2-(1-ethylpropyl)pyridine, aminopyridine, and dimethylaminopyridine),pyridazine derivatives, pyrimidine derivatives, pyrazine derivatives,pyrazoline derivatives, pyrazolidine derivatives, piperidinederivatives, piperazine derivatives, morpholine derivatives, indolederivatives, isoindole derivatives, 1H-indazole derivatives, indolinederivatives, quinoline derivatives (e.g., quinoline and3-quinolinecarbonitrile), isoquinoline derivatives, cinnolinederivatives, quinazoline derivatives, quinoxaline derivatives,phthalazine derivatives, purine derivatives, pteridine derivatives,carbazole derivatives, phenanthridine derivatives, acridine derivatives,phenazine derivatives, 1,10-phenanthroline derivatives, adeninederivatives, adenosine derivatives, guanine derivatives, guanosinederivatives, uracil derivatives, and uridine derivatives.

Examples of suitable nitrogen-containing compounds having carboxyl groupinclude aminobenzoic acid, indolecarboxylic acid, and amino acidderivatives (e.g., nicotinic acid, alanine, alginine, aspartic acid,glutamic acid, glycine, histidine, isoleucine, glycylleucine, leucine,methionine, phenylalanine, threonine, lysine,3-aminopyrazine-2-carboxylic acid, and methoxyalanine). Examples ofsuitable nitrogen-containing compounds having sulfonyl group include3-pyridinesulfonic acid and pyridinium p-toluenesulfonate. Examples ofsuitable nitrogen-containing compounds having hydroxyl group,nitrogen-containing compounds having hydroxyphenyl group, andnitrogen-containing alcoholic compounds include 2-hydroxypyridine,aminocresol, 2,4-quinolinediol, 3-indolemethanol hydrate,monoethanolamine, diethanolamine, triethanolamine,N-ethyldiethanolamine, N,N-diethylethanolamine, triisopropanolamine,2,2′-iminodiethanol, 2-aminoethanol, 3-amino-1-propanol,4-amino-1-butanol, 4-(2-hydroxyethyl)morpholine,2-(2-hydroxyethyl)pyridine, 1-(2-hydroxyethyl)piperazine,1-[2-(2-hydroxyethoxy)ethyl]piperazine, piperidine ethanol,1-(2-hydroxyethyl)pyrrolidine, 1- (2-hydroxyethyl)-2-pyrrolidinone,3-piperidino-1,2-propanediol, 3-pyrrolidino-1,2-propanediol,8-hydroxyjulolidine, 3-quinuclidinol, 3-tropanol, 1-methyl-2-pyrrolidineethanol, 1-aziridine ethanol, N-(2-hydroxyethyl)phthalimide, andN-(2-hydroxyethyl)isonicotinamide. Examples of suitable amidederivatives include formamide, N-methylformamide, N,N-dimethylformamide,acetamide, N-methylacetamide, N,N-dimethylacetamide, propionamide, andbenzamide. Suitable imide derivatives include phthalimide, succinimide,and maleimide.

One or more basic compounds of the following general formula (B)-1 mayalso be added.N(X)_(n)(Y)_(3-n)  (B)-1

In the formula, n is equal to 1, 2 or 3; side chain Y is independentlyhydrogen or a straight, branched or cyclic alkyl group of 1 to 20,carbonatoms which may contain an ether or hydroxyl group; and side chain X isindependently selected from groups of the following general formulas(X)-1 to (X)-3, and two or three X's may bond together to form a ring.

In the formulas, R³⁰⁰, R³⁰² and R³⁰⁵ are independently straight orbranched alkylene groups of 1 to 4 carbon atoms; R³⁰¹ and R³⁰⁴ areindependently hydrogen, straight, branched or cyclic alkyl groups of 1to 20 carbon atoms, which may contain at least one hydroxyl, ether,ester group or lactone ring; R³⁰³ is a single bond or a straight orbranched alkylene group of 1 to 4 carbon atoms; and R³⁰⁶ is a straight,branched or cyclic alkyl group of 1 to 20 carbon atoms, which maycontain at least one hydroxyl, ether, ester group or lactone ring.

Illustrative examples of the compounds of formula (B)-1 includetris(2-methoxymethoxyethyl)amine,

-   tris{2-(2-methoxyethoxy)ethyl}amine,-   tris{2-(2-methoxyethoxymethoxy)ethyl}amine,-   tris{2-(1-methoxyethoxy)ethyl}amine,-   tris{2-(1-ethoxyethoxy)ethyl}amine,-   tris{2-(1-ethoxypropoxy)ethyl}amine,-   tris[2-{2-(2-hydroxyethoxy)ethoxy}ethyl]amine,-   4,7,13,16,21,24-hexaoxa-1,10-diazabicyclo[8.8.8]hexacosane,-   4,7,13,18-tetraoxa-1,10-diazabicyclo[8.5.5]eicosane,-   1,4,10,13-tetraoxa-7,16-diazabicyclooctadecane,-   1-aza-12-crown-4,1-aza-15-crown-5,1-aza-18-crown-6,-   tris(2-formyloxyethyl)amine, tris(2-acetoxyethyl)amine,-   tris(2-propionyloxyethyl)amine, tris(2-butyryloxyethyl)amine,-   tris(2-isobutyryloxyethyl)amine, tris(2-valeryloxyethyl)amine,-   tris(2-pivaloyloxyethyl)amine,-   N,N-bis(2-acetoxyethyl)-2-(acetoxyacetoxy)ethylamine,-   tris(2-methoxycarbonyloxyethyl)amine,-   tris(2-tert-butoxycarbonyloxyethyl)amine,-   tris[2-(2-oxopropoxy)ethyl]amine,-   tris[2-(methoxycarbonylmethyl)oxyethyl]amine,-   tris[2-(tert-butoxycarbonylmethyloxy)ethyl]amine,-   tris[2-(cyclohexyloxycarbonylmethyloxy)ethyl]amine,-   tris(2-methoxycarbonylethyl)amine,-   tris(2-ethoxycarbonylethyl)amine,-   N-N-bis(2-hydroxyethyl)-2-(methoxycarbonyl)ethylamine,-   N-N-bis(2-acetoxyethyl)-2-(methoxycarbonyl)ethylamine,-   N-N-bis(2-hydroxyethyl)-2-(ethoxycarbonyl)ethylamine,-   N-N-bis(2-acetoxyethyl)-2-(ethoxycarbonyl)ethylamine,-   N-N-bis(2-hydroxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,-   N-N-bis(2-acetoxyethyl)-2-(2-methoxyethoxycarbonyl)ethylamine,-   N-N-bis(2-hydroxyethyl)-2-(2-hydroxyethoxycarbonyl)ethylamine,-   N-N-bis(2-acetoxyethyl)-2-(2-acetoxyethoxycarbonyl)ethylamine,-   N-N-bis(2-hydroxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylamine,-   N-N-bis(2-acetoxyethyl)-2-[(methoxycarbonyl)methoxycarbonyl]-ethylamine,-   N-N-bis(2-hydroxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,-   N-N-bis(2-acetoxyethyl)-2-(2-oxopropoxycarbonyl)ethylamine,-   N-N-bis(2-hydroxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)-ethylamine,-   N-N-bis(2-acetoxyethyl)-2-(tetrahydrofurfuryloxycarbonyl)-ethylamine,-   N-N-bis(2-hydroxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxy-carbonyl]ethylamine,-   N-N-bis(2-acetoxyethyl)-2-[(2-oxotetrahydrofuran-3-yl)oxy-carbonyl]ethylamine,-   N-N-bis(2-hydroxyethyl)-2-(4-hydroxybutoxycarbonyl)ethylamine,-   N-N-bis(2-formyloxyethyl)-2-(4-formyloxybutoxycarbonyl)-ethylamine,-   N-N-bis(2-formyloxyethyl)-2-(2-formyloxyethoxycarbonyl)-ethylamine,-   N-N-bis(2-methoxyethyl)-2-(methoxycarbonyl)ethylamine,-   N-(2-hydroxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,-   N-(2-acetoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,-   N-(2-hydroxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,-   N-(2-acetoxyethyl)-bis[2-(ethoxycarbonyl)ethyl]amine,-   N-(3-hydroxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,-   N-(3-acetoxy-1-propyl)-bis[2-(methoxycarbonyl)ethyl]amine,-   N-(2-methoxyethyl)-bis[2-(methoxycarbonyl)ethyl]amine,-   N-butyl-bis[2-(methoxycarbonyl)ethyl]amine,-   N-butyl-bis[2-(2-methoxyethoxycarbonyl)ethyl]amine,-   N-methyl-bis(2-acetoxyethyl)amine,-   N-ethyl-bis(2-acetoxyethyl)amine,-   N-methyl-bis(2-pivaloyloxyethyl)amine,-   N-ethyl-bis[2-(methoxycarbonyloxy)ethyl]amine,-   N-ethyl-bis[2-(tert-butoxycarbonyloxy)ethyl]amine,-   tris(methoxycarbonylmethyl)amine,-   tris(ethoxycarbonylmethyl)amine,-   N-butyl-bis(methoxycarbonylmethyl)amine,-   N-hexyl-bis(methoxycarbonylmethyl)amine, and-   β-(diethylamino)-δ-valerolactone.

Also useful are basic compounds having cyclic structure, represented bythe following general formula (B)-2.

Herein X is as defined above, and R³⁰⁷ is a straight or branchedalkylene group of 2 to 20 carbon atoms which may contain one or morecarbonyl, ether, ester or sulfide groups.

Illustrative examples of the compounds having formula (B)-2 include1-[2-(methoxymethoxy)ethyl]pyrrolidine,

-   1-[2-(methoxymethoxy)ethyl]piperidine,-   4-[2-(methoxymethoxy)ethyl]morpholine,-   1- [2-[(2-methoxyethoxy)methoxy]ethyl]pyrrolidine,-   1-[2-[(2-methoxyethoxy)methoxy]ethyl]piperidine,-   4-[2-[(2-methoxyethoxy)methoxy]ethyl]morpholine,-   2-(1-pyrrolidinyl)ethyl acetate, 2-piperidinoethyl acetate,-   2-morpholinoethyl acetate, 2-(1-pyrrolidinyl)ethyl formate,-   2-piperidinoethyl propionate,-   2-morpholinoethyl acetoxyacetate,-   2-(1-pyrrolidinyl)ethyl methoxyacetate,-   4-[2-(methoxycarbonyloxy)ethyl]morpholine,-   1-[2-(t-butoxycarbonyloxy)ethyl]piperidine,-   4-[2-(2-methoxyethoxycarbonyloxy)ethyl]morpholine,-   methyl 3-(1-pyrrolidinyl)propionate,-   methyl 3-piperidinopropionate, methyl 3-morpholinopropionate,-   methyl 3-(thiomorpholino)propionate,-   methyl 2-methyl-3-(1-pyrrolidinyl)propionate,-   ethyl 3-morpholinopropionate,-   methoxycarbonylmethyl 3-piperidinopropionate,-   2-hydroxyethyl 3-(1-pyrrolidinyl)propionate,-   2-acetoxyethyl 3-morpholinopropionate,-   2-oxotetrahydrofuran-3-yl 3-(1-pyrrolidinyl)propionate,-   tetrahydrofurfuryl 3-morpholinopropionate,-   glycidyl 3-piperidinopropionate,-   2-methoxyethyl 3-morpholinopropionate,-   2-(2-methoxyethoxy)ethyl 3-(1-pyrrolidinyl)propionate,-   butyl 3-morpholinopropionate,-   cyclohexyl 3-piperidinopropionate,-   α-(l-pyrrolidinyl)methyl-γ-butyrolactone,-   β-piperidino-γ-butyrolactone, β-morpholino-δ-valerolactone,-   methyl 1-pyrrolidinylacetate, methyl piperidinoacetate,-   methyl morpholinoacetate, methyl thiomorpholinoacetate,-   ethyl 1-pyrrolidinylacetate, and-   2-methoxyethyl morpholinoacetate.

Also, basic compounds having cyano group, represented by the followinggeneral formulae (B)-3 to (B)-6 are useful.

Herein, X, R³⁰⁷ and n are as defined above, and R³⁰⁸ and R³⁰⁹ are eachindependently a straight or branched alkylene group of 1 to 4 carbonatoms.

Illustrative examples of the basic compounds having cyano group,represented by formulae (B)-3 to (B)-6, include3-(diethylamino)propiononitrile,

-   N-N-bis(2-hydroxyethyl)-3-aminopropiononitrile,-   N-N-bis(2-acetoxyethyl)-3-aminopropiononitrile,-   N-N-bis(2-formyloxyethyl)-3-aminopropiononitrile,-   N-N-bis(2-methoxyethyl)-3-aminopropiononitrile,-   N-N-bis[2-(methoxymethoxy)ethyl]-3-aminopropiononitrile,-   methyl N-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropionate,-   methyl N-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropionate,-   methyl N-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropionate,-   N-(2-cyanoethyl)-N-ethyl-3-aminopropiononitrile,-   N-(2-cyanoethyl)-N-(2-hydroxyethyl)-3-aminopropiononitrile,-   N-(2-acetoxyethyl)-N-(2-cyanoethyl)-3-aminopropiononitrile,-   N-(2-cyanoethyl)-N-(2-formyloxyethyl)-3-aminopropiononitrile,-   N-(2-cyanoethyl)-N-(2-methoxyethyl)-3-aminopropiononitrile,-   N-(2-cyanoethyl)-N-[2-(methoxymethoxy)ethyl]-3-aminopropiono-nitrile,-   N-(2-cyanoethyl)-N-(3-hydroxy-1-propyl)-3-aminopropiono-nitrile,-   N-(3-acetoxy-1-propyl)-N-(2-cyanoethyl)-3-aminopropiono-nitrile,-   N-(2-cyanoethyl)-N-(3-formyloxy-1-propyl)-3-aminopropiono-nitrile,-   N-(2-cyanoethyl)-N-tetrahydrofurfuryl-3-aminopropiononitrile,-   N-N-bis(2-cyanoethyl)-3-aminopropiononitrile,-   diethylaminoacetonitrile,-   N-N-bis(2-hydroxyethyl)aminoacetonitrile,-   N-N-bis(2-acetoxyethyl)aminoacetonitrile,-   N-N-bis(2-formyloxyethyl)aminoacetonitrile,-   N-N-bis(2-methoxyethyl)aminoacetonitrile,-   N-N-bis[2-(methoxymethoxy)ethyl]aminoacetonitrile,-   methyl N-cyanomethyl-N-(2-methoxyethyl)-3-aminopropionate,-   methyl N-cyanomethyl-N-(2-hydroxyethyl)-3-aminopropionate,-   methyl N-(2-acetoxyethyl)-N-cyanomethyl-3-aminopropionate,-   N-cyanomethyl-N-(2-hydroxyethyl)aminoacetonitrile,-   N-(2-acetoxyethyl)-N-(cyanomethyl)aminoacetonitrile,-   N-cyanomethyl-N-(2-formyloxyethyl)aminoacetonitrile,-   N-cyanomethyl-N-(2-methoxyethyl)aminoacetonitrile,-   N-cyanomethyl-N-[2-(methoxymethoxy)ethyl)aminoacetonitrile,-   N-cyanomethyl-N-(3-hydroxy-1-propyl)aminoacetonitrile,-   N-(3-acetoxy-1-propyl)-N-(cyanomethyl)aminoacetonitrile,-   N-cyanomethyl-N-(3-formyloxy-1-propyl)aminoacetonitrile,-   N-N-bis(cyanomethyl)aminoacetonitrile,-   1-pyrrolidinepropiononitrile, 1-piperidinepropiononitrile,-   4-morpholinepropiononitrile, 1-pyrrolidineacetonitrile,-   1-piperidineacetonitrile, 4-morpholineacetonitrile,-   cyanomethyl 3-diethylaminopropionate,-   cyanomethyl N,N-bis(2-hydroxyethyl)-3-aminopropionate,-   cyanomethyl N,N-bis(2-acetoxyethyl)-3-aminopropionate,-   cyanomethyl N,N-bis(2-formyloxyethyl)-3-aminopropionate,-   cyanomethyl N,N-bis(2-methoxyethyl)-3-aminopropionate,-   cyanomethyl N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate,-   2-cyanoethyl 3-diethylaminopropionate,-   2-cyanoethyl N,N-bis(2-hydroxyethyl)-3-aminopropionate,-   2-cyanoethyl N,N-bis(2-acetoxyethyl)-3-aminopropionate,-   2-cyanoethyl N,N-bis(2-formyloxyethyl)-3-aminopropionate,-   2-cyanoethyl N,N-bis(2-methoxyethyl)-3-aminopropionate,-   2-cyanoethyl N,N-bis[2-(methoxymethoxy)ethyl]-3-aminopropionate,-   cyanomethyl 1-pyrrolidinepropionate,-   cyanomethyl 1-piperidinepropionate,-   cyanomethyl 4-morpholinepropionate,-   2-cyanoethyl 1-pyrrolidinepropionate,-   2-cyanoethyl 1-piperidinepropionate, and-   2-cyanoethyl 4-morpholinepropionate.

The basic compound is preferably formulated in an amount of 0.001 to 2parts, and especially 0.01 to 1 part by weight, per 100 parts by weightof the base resin. Less than 0.001 part of the basic compound achievesno or little addition effect whereas more than 2 parts would result intoo low a sensitivity.

Other Components

In the positive resist composition, a compound having a group ≡C-COOH inthe molecule may be blended. Exemplary, non-limiting compounds having acarboxyl group include one or more compounds selected from Groups I andII below. Including this compound improves the PED stability of theresist and ameliorates edge roughness on nitride film substrates.

Group I:

Compounds in which some or all of the hydrogen atoms on the phenolichydroxyl groups of the compounds of general formulas (A1) to (A10) belowhave been replaced by —R⁴⁰¹—COOH (wherein R⁴⁰¹ is a straight or branchedalkylene of 1 to 10 carbon atoms), and in which the molar ratio C/(C+D)of phenolic hydroxyl groups (C) to ≡C—COOH groups (D) in the molecule isfrom 0.1 to 1.0.

In these formulas, R⁴⁰⁸ is hydrogen or methyl; R⁴⁰² and R⁴⁰³ are eachhydrogen or a straight or branched C₁-C₈ alkyl or alkenyl; R⁴⁰⁴ ishydrogen, a straight or branched C₁-C₈ alkyl or alkenyl, or a—(R⁴⁰⁹)_(h)—COOR′ group (R′ being hydrogen or —R⁴⁰⁹—COOH); R⁴⁰⁵ is—(CH₂)_(i)— (wherein i is 2 to 10), a C₆-C₁₀ arylene, carbonyl,sulfonyl, an oxygen atom, or a sulfur atom; R⁴⁰⁶ is a C₁-C₁₀ alkylene, aC₆-C₁₀ arylene, carbonyl, sulfonyl, an oxygen atom, or a sulfur atom;R⁴⁰⁷ is hydrogen, a straight or branched C₁-C₈ alkyl or alkenyl, or ahydroxyl-substituted phenyl or naphthyl; R⁴⁰⁹ is a straight or branchedC₁-C₁₀ alkyl or alkenyl or a —R⁴¹¹—COOH group; R⁴¹⁰ is hydrogen, astraight or branched C₁-C₈ alkyl or alkenyl, or a —R⁴¹¹—COOH group; R⁴¹¹is a straight or branched C₁-C₁₀ alkylene; h is an integer of 1 to 4, jis an integer from 0 to 3; s1, t1, s2, t2, s3, t3, s4, and t4 are eachnumbers which satisfy s1+t1=8, s2+t2=5, s3+t3=4, and s4+t4 =6, and aresuch that each phenyl structure has at least one hydroxyl group; u is aninteger of 1 to 4; κ is a number such that the compound of formula (A6)may have a weight average molecular weight of 1,000 to 5,000; and λ is anumber such that the compound of formula (A7) may have a weight averagemolecular weight of 1,000 to 10,000.

Group II:

Compounds of general formulas (A11) to (A15) below.

In these formulas, R⁴⁰², R⁴⁰³, and R⁴¹¹ are as defined above; R⁴¹² ishydrogen or hydroxyl; s5 and t5 are numbers which satisfy s5 ≧0, t5≧0,and s5+t5=5; and h′ is 0 or 1.

Illustrative, non-limiting examples of the compound having a carboxylgroup include compounds of the general formulas AI-1 to AI-14 and AII-1to AII-10 below.

In the above formulas, R″ is hydrogen or a —CH₂COOH group such that the—CH₂COOH group accounts for 10 to 100 mol % of R″ in each compound, κand λ are as defined above.

The compound is added in an amount ranging from 0 to 5 parts, preferably0.1 to 5 parts, more preferably 0.1 to 3 parts, further preferably 0.1to 2 parts by weight, per 100 parts by weight of the base resin. Morethan 5 parts of the compound can reduce the resolution of the resistcomposition.

The positive resist composition of the invention may further include asurfactant which is commonly used for improving the coatingcharacteristics.

Illustrative, non-limiting, examples of the surfactant include nonionicsurfactants, for example, polyoxyethylene alkyl ethers such aspolyoxyethylene lauryl ether, polyoxyethylene stearyl ether,polyoxyethylene cetyl ether, and polyoxyethylene oleyl ether,polyoxyethylene alkylaryl ethers such as polyoxyethylene octylphenolether and polyoxyethylene nonylphenol ether, polyoxyethylenepolyoxypropylene block copolymers, sorbitan fatty acid esters such assorbitan monolaurate, sorbitan monopalmitate, and sorbitan monostearate,and polyoxyethylene sorbitan fatty acid esters such as polyoxyethylenesorbitan monolaurate, polyoxyethylene sorbitan monopalmitate,polyoxyethylene sorbitan monostearate, polyoxyethylene sorbitantrioleate, and polyoxyethylene sorbitan tristearate; fluorochemicalsurfactants such as EFTOP EF301, EF303 and EF352 (Tohkem Products Co.,Ltd.), Megaface F171, F172 and F173 (Dai-Nippon Ink & Chemicals, Inc.),Fluorad FC430 and FC431 (Sumitomo 3M Co., Ltd.), Asahiguard AG710,Surflon S-381, S-382, SC101, SC102, SC103, SC104, SC105, SC106, SurfynolE1004, KH-10, KH-20, KH-30 and KH-40 (Asahi Glass Co., Ltd.);organosiloxane polymers KP341, X-70-092 and X-70-093 (Shin-Etsu ChemicalCo., Ltd.), acrylic acid or methacrylic acid Polyflow No. 75 and No. 95(Kyoeisha Ushi Kagaku Kogyo Co., Ltd.). Inter alia, FC430, SurflonS-381, Surfynol E1004, KH-20 and KH-30 are preferred. These surfactantsmay be used alone or in admixture.

To the positive resist composition, the surfactant is added in an amountof up to 2 parts, preferably up to 1 part by weight, per 100 parts byweight of the base resin.

For the microfabrication of integrated circuits, any well-knownlithography may be used to form a resist pattern from the positiveresist composition of the invention, especially the chemically amplifiedpositive resist composition comprising the polymer, organic solvent,photoacid generator and optional components according to the inventionalthough the technology is not limited thereto.

The composition is applied onto a substrate (on which an integratedcircuit is to be formed, e.g., Si, SiO₂, SiN, SiON, TiN, WSi, BPSG, SOG,organic antireflective film, Cr, CrO, CrON, MoSi, etc.) by a suitablecoating technique such as spin coating, roll coating, flow coating, dipcoating, spray coating or doctor coating. The coating is prebaked on ahot plate at a temperature of 60 to 150° C. for about 1 to 10 minutes,preferably 80 to 120° C. for 1 to 5 minutes. The resulting resist filmis generally 0.1 to 2.0 μm thick. With a mask having a desired patternplaced above the resist film, the resist film is then exposed to actinicradiation such as UV, deep-UV, electron beams, x-rays, excimer laserlight, γ-rays and synchrotron radiation, preferably having an exposurewavelength of up to 300 nm, more preferably 180 to 200 nm. The exposuredose is preferably about 1 to 200 mJ/cm², more preferably about 10 to100 mJ/cm². The film is further baked on a hot plate at 60 to 150° C.for 1 to 5 minutes, preferably 80 to 120° C. for 1 to 3 minutes(post-exposure baking=PEB).

Thereafter the resist film is developed with a developer in the form ofan aqueous base solution, for example, 0.1 to 5 wt %, preferably 2 to 3wt % aqueous solution of tetramethylammonium hydroxide (TMAH) for 0.1 to3 minutes, preferably 0.5 to 2 minutes by conventional techniques suchas dip, puddle or spray techniques. In this way, a desired resistpattern is formed on the substrate. It is appreciated that the resistcomposition of the invention is suited for micro-patterning using suchhigh-energy radiation as deep UV with a wavelength of 254 to 193 nm,vacuum UV with a wavelength of 157 nm, electron beams, soft x-rays,x-rays, excimer laser light, γ-rays and synchrotron radiation, and bestsuitable for micro-patterning using high-energy radiation in thewavelength range of up to 200 nm, especially 180 to 200 nm.

Immersion lithography can be applied to the resist composition of theinvention. The ArF immersion lithography uses deionized water as theimmersion solvent. The immersion lithography involves prebaking a resistfilm and exposing the resist film to light through a projection lens,with water interposed between the resist film and the projection lens.Since the immersion lithography increases the numerical aperture (NA) ofthe projection lens to 1.0 or higher and improves resolution, it isimportant for the ArF lithography to survive to the 65-nm node, with afurther development thereof being accelerated. The lactone ring, whichis used as a hydrophilic group in the prior art ArF resists, hassolubility in both alkaline aqueous solution and water. When lactonesand acid anhydrides (e.g., maleic anhydride and itaconic anhydride)having high solubility in water are used as the hydrophilic group, aproblem arises during immersion in water that more water penetrates intothe resist from its surface, whereby the resist surface is swollen. Bycontrast, hydroxynaphthalene is dissolvable in alkaline aqueoussolution, but not at all in water, and it is thus believed that theinfluence of dissolution and swelling during liquid immersion isminimized.

EXAMPLE

Examples of the invention are given below by way of illustration and notby way of limitation. The abbreviations used herein are AIBN for2,2′-azobisisobutyronitrile, GPC for gel permeation chromatography, NMRfor nuclear magnetic resonance, Mw for weight average molecular weight,Mn for number average molecular weight, Mw/Mn for molecular weightdistribution or dispersity, and PGMEA for propylene glycol monomethylether acetate. For all polymers, Mw and Mn are determined by GPC versuspolystyrene standards.

Synthesis Example 1

A 100-mL flask was charged with 8.2 g of3-ethyl-3-exo-tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodecanyl methacrylate,9.0 g of 3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate,6.8 g of 5-hydroxy-1-naphthyl methacrylate, and 30 g of tetrahydrofuranas a solvent. The reactor was subjected to cooling to −70° C. in anitrogen atmosphere, evacuation to vacuum, and nitrogen flow, whichprocedure was repeated three times. The reactor was warmed up to roomtemperature, charged with 0.2 g of AIBN as a polymerization initiator,heated at 60° C., and held for 15 hours for reaction. The reactionsolution was poured into 500 mL of isopropyl alcohol for precipitation.The white solids were collected by filtration and dried at 60° C. underreduced pressure, yielding 21.8 g of a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

3-ethyl-3-exo-tetracyclo[4.4.0.1^(2,5).1^(7,10)]dodecanyl methacrylate:3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate:5-hydroxy-1-naphthyl methacrylate=0.30:0.40:0.30

Mw=8,900

Mw/Mn=1.72

This polymer is designated Inventive Polymer 1.

Synthesis Example 2

A 100-mL flask was charged with 8.7 g of 2-ethyl-2-adamantanemethacrylate, 5.0 g of 3-hydroxy-1-adamantyl methacrylate, 5.6 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate, 4.6 g of5-hydroxy-1-naphthyl methacrylate, and 30 g of tetrahydrofuran as asolvent. The reactor was subjected to cooling to −70° C. in a nitrogenatmosphere, evacuation to vacuum, and nitrogen flow, which procedure wasrepeated three times. The reactor was warmed up to room temperature,charged with 0.2 g of AIBN as a polymerization initiator, heated at 60°C., and held for 15 hours for reaction. The reaction solution was pouredinto 500 mL of isopropyl alcohol for precipitation. The white solidswere collected by filtration and dried at 60° C. under reduced pressure,yielding 21.3 g of a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

2-ethyl-2-adamantane methacrylate: 3-hydroxy-1-adamantyl methacrylate:3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate:5-hydroxy-1-naphthyl methacrylate=0.35:0.20:0.25:0.20

Mw=8,900

Mw/Mn=1.78

This polymer is designated Inventive Polymer 2.

Synthesis Example 3

A 100-mL flask was charged with 8.7 g of 2-ethyl-2-adamantanemethacrylate, 5.0 g of 3-hydroxy-1-adamantyl methacrylate, 7.0 g of3-oxo-5-methoxycarbonyl-2-oxatricyclo[4.2.1.0^(4,8)]-nonyl methacrylate,4.6 g of 4-hydroxy-1-naphthyl methacrylate, and 30 g of tetrahydrofuranas a solvent. The reactor was subjected to cooling to −70° C. in anitrogen atmosphere, evacuation to vacuum, and nitrogen flow, whichprocedure was repeated three times. The reactor was warmed up to roomtemperature, charged with 0.2 g of AIBN as a polymerization initiator,heated at 60° C., and held for 15 hours for reaction. The reactionsolution was poured into 500 mL of isopropyl alcohol for precipitation.The white solids were collected by filtration and dried at 60° C. underreduced pressure, yielding 22.3 g of a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

2-ethyl-2-adamantane methacrylate: 3-hydroxy-1-adamantyl methacrylate:3-oxo-5-methoxycarbonyl-2-oxatricyclo[4.2.1.0^(4,8)]-9-nonylmethacrylate: 4-hydroxy-1-naphthyl methacrylate=0.35:0.20:0.25:0.20

Mw=7,700

Mw/Mn=1.73

This polymer is designated Inventive Polymer 3.

Synthesis Example 4

A 100-mL flask was charged with 5.2 g of 1-cyclohexylcyclopentylmethacrylate, 5.0 g of 3-hydroxy-1-adamantyl methacrylate, 9.1 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate, 4.6 g of5-hydroxy-1-naphthyl methacrylate, and 30 g of tetrahydrofuran as asolvent. The reactor was subjected to cooling to −70° C. in a nitrogenatmosphere, evacuation to vacuum, and nitrogen flow, which procedure wasrepeated three times. The reactor was warmed up to room temperature,charged with 0.2 g of AIBN as a polymerization initiator, heated at 60°C., and held for 15 hours for reaction. The reaction solution was pouredinto 500 mL of isopropyl alcohol for precipitation. The white solidswere collected by filtration and dried at 60° C. under reduced pressure,yielding 21.0 g of a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

1-cyclohexylcyclopentyl methacrylate: 3-hydroxy-1-adamantylmethacrylate: 3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-ylmethacrylate: 5-hydroxy-1-naphthyl methacrylate=0.22:0.20:0.38:0.20

Mw=7,800

Mw/Mn=1.73

This polymer is designated Inventive Polymer 4.

Synthesis Example 5

A 100-mL flask was charged with 6.0 g of 1-ethylcyclopentylmethacrylate, 3.6 g of 3-hydroxy-1-adamantyl methacrylate, 6.6 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate, 5.7 g of5-hydroxy-1-naphthyl methacrylate, and 30 g of tetrahydrofuran as asolvent. The reactor was subjected to cooling to −70° C. in a nitrogenatmosphere, evacuation to vacuum, and nitrogen flow, which procedure wasrepeated three times. The reactor was warmed up to room temperature,charged with 0.2 g of AIBN as a polymerization initiator, heated at 60°C., and held for 15 hours for reaction. The reaction solution was pouredinto 500 mL of isopropyl alcohol for precipitation. The white solidswere collected by filtration and dried at 60° C. under reduced pressure,yielding 18.7 g of a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

1-ethylcyclopentyl methacrylate: 3-hydroxy-1-adamantyl methacrylate:3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate:5-hydroxy-1-naphthyl methacrylate=0.33:0.15:0.27:0.25

Mw=8,500

Mw/Mn=1.76

This polymer is designated Inventive Polymer 5.

Synthesis Example 6

A 100-mL flask was charged with 6.3 g of1-(7-oxanorbornan-2-yl)cyclopentyl methacrylate, 5.0 g of3-hydroxy-1-adamantyl methacrylate, 7.8 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate, 4.6 g of5-hydroxy-1-naphthyl methacrylate, and 30 g of tetrahydrofuran as asolvent. The reactor was subjected to cooling to −70° C. in a nitrogenatmosphere, evacuation to vacuum, and nitrogen flow, which procedure wasrepeated three times. The reactor was warmed up to room temperature,charged with 0.2 g of AIBN as a polymerization initiator, heated at 60°C., and held for 15 hours for reaction. The reaction solution was pouredinto 500 mL of isopropyl alcohol for precipitation. The white solidswere collected by filtration and dried at 60° C. under reduced pressure,yielding 20.8 g of a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

1-(7-oxanorbornan-2-yl)cyclopentyl methacrylate: 3-hydroxy-1-adamantylmethacrylate: 3-oxo-2,7-dioxatricyclo-[4.2.1.0^(4,8)]nonan-9-ylmethacrylate: 5-hydroxy-1-naphthyl methacrylate=0.25:0.20:0.35:0.20

Mw=7,800

Mw/Mn=1.88

This polymer is designated Inventive Polymer 6.

Synthesis Example 7

A 100-mL flask was charged with 5.0 g of 2-adamantyloxymethylmethacrylate, 6.3 g of 3-hydroxy-1-adamantyl methacrylate, 6.7 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate, 5.7 g of5-hydroxy-1-naphthyl methacrylate, and 30 g of tetrahydrofuran as asolvent. The reactor was subjected to cooling to −70° C. in a nitrogenatmosphere, evacuation to vacuum, and nitrogen flow, which procedure wasrepeated three times. The reactor was warmed up to room temperature,charged with 0.2 g of AIBN as a polymerization initiator, heated at 60°C., and held for 15 hours for reaction. The reaction solution was pouredinto 500 mL of isopropyl alcohol for precipitation. The white solidswere collected by filtration and dried at 60° C. under reduced pressure,yielding 20.6 g of a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

2-adamantyloxymethyl methacrylate: 3-hydroxy-1-adamantyl methacrylate:3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate:5-hydroxy-1-naphthyl methacrylate=0.21:0.25:0.29:0.25

Mw=9,100

Mw/Mn=1.83

This polymer is designated Inventive Polymer 7.

Synthesis Example 8

A 100-mL flask was charged with 6.3 g of 3-hydroxy-1-adamantylmethacrylate, 7.8 g of 5-oxo-4-oxatricyclo[4.2.1.0^(3,7)]nonan-2-ylmethacrylate, 12.5 g of 5-t-butoxycarbonyl-1-naphthyl methacrylate, and30 g of tetrahydrofuran as a solvent. The reactor was subjected tocooling to −70° C. in a nitrogen atmosphere, evacuation to vacuum, andnitrogen flow, which procedure was repeated three times. The reactor waswarmed up to room temperature, charged with 0.2 g of AIBN as apolymerization initiator, heated at 60° C., and held for 15 hours forreaction. The reaction solution was poured into 500 mL of isopropylalcohol for precipitation. The white solids were collected by filtrationand dried at 60° C. under reduced pressure, yielding 22.8 g of a whitepolymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

3-hydroxy-1-adamantyl methacrylate:5-oxo-4-oxatricyclo-[4.2.1.0^(3,7)]nonan-2-yl methacrylate:5-t-butoxycarbonyl-1-naphthyl methacrylate=0.26:0.34:0.40

Mw=8,100

Mw/Mn=1.67

This polymer is designated Inventive Polymer 8.

Synthesis Example 9

A 100-mL flask was charged with 6.3 g of 3-hydroxy-1-adamantylmethacrylate, 8.8 g of 4-oxatricyclo[5.2.2.0^(2,8)]undecan-3-one8(9)-methacrylate, 12.5 g of 5-t-butoxycarbonyl-1-naphthyl methacrylate,and 30 g of tetrahydrofuran as a solvent. The reactor was subjected tocooling to −70° C. in a nitrogen atmosphere, evacuation to vacuum, andnitrogen flow, which procedure was repeated three times. The reactor waswarmed up to room temperature, charged with 0.2 g of AIBN as apolymerization initiator, heated at 60° C., and held for 15 hours forreaction. The reaction solution was poured into 500 mL of isopropylalcohol for precipitation. The white solids were collected by filtrationand dried at 60° C. under reduced pressure, yielding 24.0 g of a whitepolymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

3-hydroxy-1-adamantyl methacrylate:4-oxatricyclo[5.2.2.0^(2,8)]undecan-3-one 8(9)-methacrylate:5-t-butoxycarbonyl-1-naphthyl methacrylate=0.25:0.35:0.40

Mw=8,600

Mw/Mn=1.84

This polymer is designated Inventive Polymer 9.

Synthesis Example 10

A 100-mL flask was charged with 6.3 g of 3-hydroxy-1-adamantylmethacrylate, 8.8 g of spiro[methacrylic acid-5(6)-norbornane2,3′-tetrahydrofuran-2-one], 12.5 g of 5-t-butoxycarbonyl-1-naphthylmethacrylate, and 30 g of tetrahydrofuran as a solvent. The reactor wassubjected to cooling to −70° C. in a nitrogen atmosphere, evacuation tovacuum, and nitrogen flow, which procedure was repeated three times. Thereactor was warmed up to room temperature, charged with 0.2 g of AIBN asa polymerization initiator, heated at 60° C., and held for 15 hours forreaction. The reaction solution was poured into 500 mL of isopropylalcohol for precipitation. The white solids were collected by filtrationand dried at 60° C. under reduced pressure, yielding 24.6 g of a whitepolymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

3-hydroxy-1-adamantyl methacrylate: spiro[methacrylicacid-5(6)-norbornane 2,3′-tetrahydrofuran-2-one]:5-t-butoxycarbonyl-1-naphthyl methacrylate=0.25:0.35:0.40

Mw=8,900

Mw/Mn=1.72

This polymer is designated Inventive Polymer 10.

Synthesis Example 11

A 100-mL flask was charged with 14.2 g of3-ethyl-3-exotetracyclo[4.4.0.1^(2,5).1^(7,10) ]dodecanyl methacrylate,35.3 g of 1-hydroxy-5-naphthyl methacrylate, and 40 g of tetrahydrofuranas a solvent. The reactor was subjected to cooling to −70° C. in anitrogen atmosphere, evacuation to vacuum, and nitrogen flow, whichprocedure was repeated three times. The reactor was warmed up to roomtemperature, charged with 0.2 g of AIBN as a polymerization initiator,heated at 60° C., and held for 15 hours for reaction. The reactionsolution was poured into 500 mL of isopropyl alcohol for precipitation.The white solids were collected by filtration and dried at 60° C. underreduced pressure, yielding 33.8 g of a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

3-ethyl-3-exotetracyclo[4.4.0.1^(2,5).1^(7,10)]dodecanyl methacrylate:1-hydroxy-5-naphthyl methacrylate=0.25:0.75

Mw=8,900

Mw/Mn=1.45

This polymer is designated Inventive Polymer 11.

Synthesis Example 12

A 100-mL flask was charged with 14.2 g of3-ethyl-3-exotetracyclo[4.4.0.1^(2,5).1^(7,10)]dodecanyl methacrylate,14.8 g of 1-hydroxy-5-naphthyl methacrylate, 20 g of 4-hydroxystyrene,and 40 g of tetrahydrofuran as a solvent. The reactor was subjected tocooling to −70° C. in a nitrogen atmosphere, evacuation to vacuum, andnitrogen flow, which procedure was repeated three times. The reactor waswarmed up to room temperature, charged with 0.2 g of AIBN as apolymerization initiator, heated at 60° C., and held for 15 hours forreaction. The reaction solution was poured into 500 mL of isopropylalcohol for precipitation. The white solids were collected by filtrationand dried at 60° C. under reduced pressure, yielding 36.8 g of a whitepolymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

3-ethyl-3-exotetracyclo[4.4.0.1^(2,5).1^(7,10) ]dodecanyl methacrylate:1-hydroxy-5-naphthyl methacrylate: 4-hydroxystyrene=0.25:0.37:0.38

Mw=9,300

Mw/Mn=1.63

This polymer is designated Inventive Polymer 12.

Synthesis Example 13

A 100-mL flask was charged with 8.7 g of 2-ethyl-2-adamantanemethacrylate, 5.0 g of 3-hydroxy-1-adamantyl methacrylate, 5.6 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate, 4.8 g of5-carboxyl-1-naphthyl methacrylate, and 30 g of tetrahydrofuran as asolvent. The reactor was subjected to cooling to −70° C. in a nitrogenatmosphere, evacuation to vacuum, and nitrogen flow, which procedure wasrepeated three times. The reactor was warmed up to room temperature,charged with 0.2 g of AIBN as a polymerization initiator, heated at 60°C., and held for 15 hours for reaction. The reaction solution was pouredinto 500 mL of isopropyl alcohol for precipitation. The white solidswere collected by filtration and dried at 60° C. under reduced pressure,yielding 21.3 g of a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

2-ethyl-2-adamantane methacrylate: 3-hydroxy-1-adamantyl methacrylate:3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate:5-carboxyl-1-naphthyl methacrylate=0.35:0.20:0.25:0.20

Mw=8,600

Mw/Mn=1.76

This polymer is designated Inventive Polymer 13.

Synthesis Example 14

A 100-mL flask was charged with 6.8 g of3-ethyl-3-exotetracyclo[4.4.0.1^(2,5).1^(7,10)]dodecanyl methacrylate,5.9 g of 3-hydroxy-1-adamantyl methacrylate, 7.8 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate, 4.8 g of5-hydroxy-1-methylnaphthyl methacrylate, and 30 g of tetrahydrofuran asa solvent. The reactor was subjected to cooling to −70° C. in a nitrogenatmosphere, evacuation to vacuum, and nitrogen flow, which procedure wasrepeated three times. The reactor was warmed up to room temperature,charged with 0.2 g of AIBN as a polymerization initiator, heated at 60°C., and held for 15 hours for reaction. The reaction solution was pouredinto 500 mL of isopropyl alcohol for precipitation. The white solidswere collected by filtration and dried at 60° C. under reduced pressure,yielding 22.3 g of a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

3-ethyl-3-exotetracyclo[4.4.0.1^(2,5).1^(7,10)]dodecanyl methacrylate:3-hydroxy-1-adamantyl methacrylate:3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate:5-hydroxy-1-methylnaphthyl methacrylate=0.25:0.25:0.35:0.20

Mw=8,900

Mw/Mn=1.69

This polymer is designated Inventive Polymer 14.

Synthesis Example 15

A 100-mL flask was charged with 6.8 g of3-ethyl-3-exotetracyclo[4.4.0.1^(2,5).1^(7,10)]dodecanyl methacrylate,5.9 g of 3-hydroxy-1-adamantyl methacrylate, 7.8 g of3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate, 5.7 g of5-hydroxy-1-yloxycarbonylmethyl methacrylate, and 30 g oftetrahydrofuran as a solvent. The reactor was subjected to cooling to−70° C. in a nitrogen atmosphere, evacuation to vacuum, and nitrogenflow, which procedure was repeated three times. The reactor was warmedup to room temperature, charged with 0.2 g of AIBN as a polymerizationinitiator, heated at 60° C., and held for 15 hours for reaction. Thereaction solution was poured into 500 mL of isopropyl alcohol forprecipitation. The white solids were collected by filtration and driedat 60° C. under reduced pressure, yielding 23.5 g of a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

3-ethyl-3-exotetracyclo[4.4.0.1^(2,5).1^(7,10)]dodecanyl methacrylate:3-hydroxy-1-adamantyl methacrylate:3-oxo-2,7-dioxatricyclo[4.2.1.0^(4,8)]nonan-9-yl methacrylate:5-hydroxy-1-yloxycarbonylmethyl methacrylate=0.25:0.25:0.35:0.20

Mw=9,100

Mw/Mn=1.73

This polymer is designated Inventive Polymer 15.

Comparative Synthesis Example 1

A 100-mL flask was charged with 8.7 g of 2-ethyl-2-adamantanemethacrylate, 7.5 g of 3-hydroxy-1-adamantyl methacrylate, 7.3 g of5-oxo-4-oxatricyclo[4.2.1.0^(3,7)]nonan-2-yl methacrylate, and 30 g oftetrahydrofuran as a solvent. The reactor was subjected to cooling to−70° C. in a nitrogen atmosphere, evacuation to vacuum, and nitrogenflow, which procedure was repeated three times. The reactor was warmedup to room temperature, charged with 0.2 g of AIBN as a polymerizationinitiator, heated at 60° C., and held for 15 hours for reaction. Thereaction solution was poured into 500 mL of isopropyl alcohol forprecipitation. The white solids were collected by filtration and driedat 60° C. under reduced pressure, yielding 19.5 g of a white polymer.

The polymer was analyzed by ¹³C-NMR, ¹H-NMR, and GPC, with the resultsshown below.

Copolymer Composition Ratio (Molar Ratio)

2-ethyl-2-adamantane methacrylate: 3-hydroxy-1-adamantyl methacrylate:5-oxo-4-oxatricyclo[4.2.1.0^(3,7)]nonan-2-yl methacrylate=0.35:0.30:0.35

Mw=8,900

Mw/Mn=1.83

This polymer is designated Comparative Polymer 1.

Examples and Comparative Examples

Preparation of Positive Resist Compositions

Resist solutions were prepared by dissolving the polymer (InventivePolymers 1 to 10, 13 to 15 and Comparative Polymer 1) and othercomponents in a solvent in accordance with the formulation shown inTable 1 and passing through a filter with a pore size of 0.2 μm. Thecomponents in Table 1 are as follows.

Polymer:

Inventive Polymers 1 to 10 and 13 to 15

-   -   resulting from Synthesis Examples 1 to 10 and 13 to 15

Comparative Polymer 1

-   -   resulting from Comparative Synthesis Example 1        Photoacid Generator:

PAG1 to PAG4 of the following structural formulae

Basic Compound:

triethanolamine, TMMEA, AAA, and AACN of the following structuralformulae

Dissolution Inhibitor:

DRI1 of the following structural formula

Organic Solvent:

PGMEA

Exposure/Patterning

On silicon wafers which had been hexamethyldisilazane (HMDS) vaporprimed, the resist solutions (Examples 1-19, Comparative Example 1) werespin coated, then baked on a hot plate at 120° C. for 60 seconds to giveresist films having a thickness of 250 nm.

The resist films were exposed by means of an ArF excimer laser steppermodel NSR-S305B (Nikon Corp., NA 0.68, σ 0.85, ⅔ annular illumination,6% halftone phase shift mask). Immediately after exposure, the resistfilms were baked (PEB) at 110° C. for 60 seconds and then developed for60 seconds with a 2.38% aqueous solution of tetramethylammoniumhydroxide, obtaining positive patterns.

The resist patterns were evaluated. The exposure dose (mJ/cm²) whichprovided a 1:1 resolution to a 0.12-μm line-and-space pattern was thesensitivity. The minimum line width (nm) of a L/S pattern which wasascertained separate at this dose was the resolution of a test resist.Using a measuring SEM model S-9220 (Hitachi Ltd.), the 0.12-μm L/Spattern was measured for line edge roughness. A cross section of theresist was observed under a SEM model S4200 (Hitachi Ltd.). The resultsare also shown in Table 1.

TABLE 1 Photoacid Basic Dissolution Line edge generator compoundinhibitor Solvent Sensitivity Resolution Pattern roughness Polymer (pbw)(pbw) (pbw) (pbw) (pbw) (mJ/cm²) (μm) profile (3σ, nm) Example 1Inventive Polymer 1 PAG1 triethanolamine — PGMEA 32 0.11 rectangular 7.2(100) (4.5) (0.45) (800) Example 2 Inventive Polymer 2 PAG1triethanolamine — PGMEA 31 0.11 rectangular 6.1 (100) (4.5) (0.45) (800)Example 3 Inventive Polymer 3 PAG1 triethanolamine — PGMEA 35 0.11rectangular 7.8 (100) (4.5) (0.45) (800) Example 4 Inventive Polymer 4PAG1 triethanolamine — PGMEA 31 0.11 rectangular 7.6 (100) (4.5) (0.45)(800) Example 5 Inventive Polymer 5 PAG1 triethanolamine — PGMEA 26 0.11rectangular 7.9 (100) (4.5) (0.45) (800) Example 6 Inventive Polymer 6PAG1 triethanolamine — PGMEA 33 0.11 rectangular 7.2 (100) (4.5) (0.45)(800) Example 7 Inventive Polymer 7 PAG1 triethanolamine — PGMEA 22 0.11rectangular 6.9 (100) (4.5) (0.45) (800) Example 8 Inventive Polymer 8PAG1 triethanolamine — PGMEA 33 0.11 rectangular 6.8 (100) (2.5) (0.45)(800) Example 9 Inventive Polymer 9 PAG1 triethanolamine — PGMEA 32 0.11rectangular 6.8 (100) (4.5) (0.45) (800) Example 10 Inventive Polymer 10PAG1 triethanolamine — PGMEA 36 0.11 rectangular 6.8 (100) (4.5) (0.45)(800) Example 11 Inventive Polymer 13 PAG1 triethanolamine — PGMEA 390.11 rectangular 7.3 (100) (4.5) (0.45) (800) Example 12 InventivePolymer 14 PAG3 triethanolamine — PGMEA 34 0.11 rectangular 6.5 (100)(4.5) (0.45) (800) Example 13 Inventive Polymer 15 PAG4 triethanolamine— PGMEA 32 0.11 rectangular 6.5 (100) (4.5) (0.45) (800) Example 14Inventive Polymer 2 PAG1 TMMEA — PGMEA 29 0.11 rectangular 6.5 (100)(4.5) (0.6)  (800) Example 15 Inventive Polymer 2 PAG1 AAA — PGMEA 280.11 rectangular 6.8 (100) (4.5) (0.6)  (800) Example 16 InventivePolymer 2 PAG1 AACN — PGMEA 33 0.11 rectangular 6.8 (100) (4.5) (0.6) (800) Example 17 Inventive Polymer 2 PAG1 triethanolamine DRI1 PGMEA 280.11 rectangular 6.3 (100) (4.5) (0.45) (10) (800) Example 18 InventivePolymer 2 PAG1 triethanolamine — PGMEA 28 0.11 rectangular 7.6  (50)(4.5) (0.45) (800) Comparative Polymer 1  (50) Example 19 InventivePolymer 2 PAG2 triethanolamine — PGMEA 38 0.11 rectangular 8.5 (100)(5.5) (0.30) (800) Comparative Comparative Polymer 1 PAG1triethanolamine — PGMEA 28 0.12 rectangular 10.5 Example 1 (100) (4.5)(0.45) (800)

It is evident from Table 1 that the resist compositions of Examples 1 to19 exhibit a high resolution. Particularly when the underlay is a highlyreflective substrate such as silicon substrate, irregularities due togeneration of standing waves are minimized, leading to minimized lineedge roughness.

EB Writing Test

Positive resist compositions were prepared in accordance with theformulation shown in Table 2 by using the polymers synthesized above,dissolving the polymers and other components in a solvent, and filteringthrough a filter having a pore size of 0.2 μm. It is noted thatInventive Polymers 11 and 12 are obtained in Synthesis Examples 11 and12, and the other components are the same as in the foregoing Examples.

Using Clean Track Mark 5 (Tokyo Electron Ltd.), the resist solutionswere spin-coated onto 6-inch silicon substrates and pre-baked on a hotplate at 110° C. for 90 seconds to form a resist film of 100 nm thick.Using an e-beam direct writing system HL-800D by Hitachi Ltd., imagewriting was performed in a vacuum chamber at a HV voltage of 50 keV.

Immediately after the image writing, post-exposure baking (PEB) waseffected on a hot plate at 110° C. for 90 seconds, using Clean TrackMark 5 (Tokyo Electron Ltd.). This was followed by puddle development inan aqueous solution of 2.38 wt % tetramethylammonium hydroxide (TMAH)for 30 seconds, giving positive patterns.

The resulting resist patterns were evaluated. The sensitivity was theexposure dose (μC/cm²) which provided a 1:1 resolution at the top andbottom of a 0.12-μm line-and-space pattern. The minimum line width (nm)of a L/S pattern which was ascertained separate at this dose was theresolution of a test resist.

Table 2 reports the formulation of resist compositions and the resultsof sensitivity and resolution thereof upon EB writing.

TABLE 2 Photoacid generator Base Solvent Sensitivity Resolution Polymer(pbw) (pbw) (pbw) (pbw) (μC/cm²) (μm) Example 20 Inventive Polymer 11PAG1 triethanolamine PGMEA 12 0.08 (100) (10.0) (0.2) (1,000) Example 21Inventive Polymer 12 PAG1 triethanolamine PGMEA 10 0.08 (100) (10.0)(0.2) (1,000) Comparative Comparative Polymer 1 PAG1 triethanolaminePGMEA 20 0.12 Example 2 (100) (10.0) (0.2) (1,000)

The data of Table 2 demonstrate that the resist compositions of Examples20 and 21 have a high sensitivity and high resolution.

Dry Etching Test

Each polymer, 2 g, was thoroughly dissolved in 10 g of PGMEA, and passedthrough a filter having a pore size of 0.2 μm, obtaining a polymersolution. The polymer solution was spin coated onto a silicon substrateand baked, forming a polymer film of 300 nm thick. Dry etching testswere carried out on the polymer films by etching them under two sets ofconditions.

(1) CHF₃/CF₄ Gas Etching Test

Using a dry etching instrument TE-8500P (Tokyo Electron K.K.), thepolymer film was etched with CHF₃/CF₄ gas under the followingconditions. The difference in polymer film thickness before and afteretching was determined.

Chamber pressure 40.0 Pa RF power 1000 W Gap 9 mm CHF₃ gas flow rate 30ml/min CF₄ gas flow rate 30 ml/min Ar gas flow rate 100 ml/min Time 60sec(2) C1₂/BC1₃ Gas Etching Test

Using a dry etching instrument L-507D-L (Nichiden Anerba K.K.), thepolymer film was etched with C1₂/BC1₃ gas under the followingconditions. The difference in polymer film thickness before and afteretching was determined.

Chamber pressure 40.0 Pa RF power 300 W Gap 9 mm Cl₂ gas flow rate 30ml/min BCl₃ gas flow rate 30 ml/min CHF₃ gas flow rate 100 ml/min O₂ gasflow rate 2 ml/min Time 60 sec

The results of the etching tests are shown in Table 3.

TABLE 3 CHF₃/CF₄ gas Cl₂/BCl₃ gas etching rate etching rate Polymer(nm/min) (nm/min) Inventive Polymer 1 132 182 Inventive Polymer 2 138186 Inventive Polymer 3 133 168 Inventive Polymer 4 135 163 InventivePolymer 5 149 177 Inventive Polymer 6 150 203 Inventive Polymer 7 140221 Inventive Polymer 8 132 189 Inventive Polymer 9 133 182 InventivePolymer 10 128 178 Inventive Polymer 11 110 133 Inventive Polymer 12 108131 Inventive Polymer 13 141 190 Inventive Polymer 14 146 193 InventivePolymer 15 151 209 Comparative Polymer 1 158 350

As is evident from Tables 1-3, resist compositions using inventivepolymers not only exhibit an excellent sensitivity and resolution, andminimized line edge roughness, but also have good dry etching resistanceas demonstrated by a minimized difference in film thickness afteretching.

Japanese Patent Application Nos. 2005-274163 and 2006-114084 areincorporated herein by reference.

Although some preferred embodiments have been described, manymodifications and variations may be made thereto in light of the aboveteachings. It is therefore to be understood that the invention may bepracticed otherwise than as specifically described without departingfrom the scope of the appended claims.

1. A positive resist composition comprising a polymer comprising atleast recurring units of the general formulae (a) and (b):

wherein R¹ is each independently hydrogen or methyl, R² is a hydroxygroup, acid labile group-substituted hydroxy group, carboxyl group, oracid labile group-substituted carboxyl group, R³ is a lactone-containingadhesive group, X is a single bond, m is 1 or 2, a and b are numbers inthe range: 0<a<1.0 and 0<b≦0.8, said lactone-containing adhesive group,as represented by R³, being selected from the group consisting of thefollowing formulae:


2. The positive resist composition of claim 1 comprising a polymercomprising at least recurring units of the general formulae (a), (b) and(c):

wherein R¹ is each independently hydrogen or methyl, R² is a hydroxygroup, acid labile group-substituted hydroxy group, carboxyl group, oracid labile group-substituted carboxyl group, R^(3A) is alactone-containing adhesive group, R^(3B) is an acid labile group, X isa single bond, m is 1 or 2, a, b and c are numbers in the range:0<a<1.0, 0<b≦0.8, 0<c≦0.8, and 0<b+c≦0.8, said lactone-containingadhesive group, as represented by R^(3A), being selected from the groupconsisting of the following formulae:


3. The positive resist composition of claim 1, further comprising anorganic solvent and a photoacid generator, and serving as a chemicallyamplified resist composition.
 4. The resist composition of claim 3,further comprising a dissolution inhibitor.
 5. The resist composition ofclaim 3, further comprising a basic compound and/or a surfactant.
 6. Aprocess for forming a pattern comprising the steps of applying theresist composition of claim 1 onto a substrate, heat treating, exposingto high-energy radiation, and developing with a developer.
 7. Thepattern forming process of claim 6 wherein the high-energy radiation hasa wavelength of up to 200 nm.
 8. The positive resist composition ofclaim 1 which further comprises a recurring unit derived from a monomerselected from the group consisting of the following formulae:


9. The positive resist composition of claim 2 which further comprises arecurring unit derived from a monomer selected from the group consistingof the following formulae:


10. The positive resist composition of claim 2, further comprising anorganic solvent and a photoacid generator, and serving as a chemicallyamplified resist composition.
 11. The resist composition of claim 10,further comprising a dissolution inhibitor.
 12. The resist compositionof claim 10, further comprising a basic compound and/or a surfactant.13. A process for forming a pattern comprising the steps of applying theresist composition of claim 2 onto a substrate, heat treating, exposingto high-energy radiation, and developing with a developer.
 14. Thepattern forming process of claim 13 wherein the high-energy radiationhas a wavelength of up to 200 nm.